I am using magento 1.8.1 and I am getting this error
Cannot send headers; headers already sent in /home/arundua20/public_html/app/code/community/CapacityWebSolutions/Inquiry/controllers/IndexController.php, line 668
Trace:
#0 /home/arundua20/public_html/lib/Zend/Controller/Response/Abstract.php(115):    Zend_Controller_Response_Abstract->canSendHeaders(true)
#1 /home/arundua20/public_html/app/code/core/Mage/Core/Model/App.php(1246): Zend_Controller_Response_Abstract->setHeader('Content-Type', 'text/html; char...')
#2 /home/arundua20/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(80): Mage_Core_Model_App->getResponse()
#3 /home/arundua20/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(202): Mage_Core_Controller_Varien_Front->getResponse()
#4 /home/arundua20/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#5 /home/arundua20/public_html/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front->dispatch()
#6 /home/arundua20/public_html/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#7 /home/arundua20/public_html/index.php(87): Mage::run('', 'store')
#8 {main}
it is showing that error is on line 668 but in that file coding is upto 327 line only.
class CapacityWebSolutions_Inquiry_IndexController extends Mage_Core_Controller_Front_Action
    {   
        public function indexAction()
        {
            $this->loadLayout(array('default'));
            $this->renderLayout();
        }
        public function delAction()
        {
            $getUrl=Mage::getSingleton('adminhtml/url')->getSecretKey("adminhtml_mycontroller","delAction");
            $delid = $this->getRequest()->getParam('delid');
            if(!empty($delid))
            {
                $collection = Mage::getModel("inquiry/inquiry")->load($delid);
                if($collection->delete())
                {
                }
                else
                {
                    Mage::getSingleton('core/session')->addError("Sorry inquiry is not deleted.");
                }
            }
            $this->_redirectReferer();
        }
        public function thanksAction()
        {
            $this->loadLayout(array('default'));
            $this->renderLayout();
            if($_POST['SUBMIT']=='SUBMIT')
            {
            $captcha =  $this->getRequest()->getParam("captcha");
            $captcha_code =  $this->getRequest()->getParam("captcha_code");
            if($captcha == $captcha_code)
            {        
            $fname =  $this->getRequest()->getParam("fname");
            $lname =  $this->getRequest()->getParam("lname");
            $company =  $this->getRequest()->getParam("company");
            $taxvat =  $this->getRequest()->getParam("account_taxvat"); 
            $address =  $this->getRequest()->getParam("address");
            $city =  $this->getRequest()->getParam("city");
            $state =  $this->getRequest()->getParam("state_id");
            $country =  $this->getRequest()->getParam("country");
            $zip =  $this->getRequest()->getParam("zip");
            $phone =  $this->getRequest()->getParam("phone");
            $email =  $this->getRequest()->getParam("email");
            $storeid = Mage::app()->getStore()->getStoreId();
            $website =  $this->getRequest()->getParam("website");
            $bdesc =  addslashes($this->getRequest()->getParam("bdesc"));
            $headers = "";
            $country1 = explode('$$$',$country);
            $resource = Mage::getSingleton('core/resource');
            $readConnection = $resource->getConnection('core_read');
            $query = 'SELECT * FROM ' . $resource->getTableName('dealerinquiry')." where email='".$email."' and storeid='".$storeid."'";
            $results = $readConnection->fetchRow($query);
              if($results == false)
              {
            $insertArr = array("firstname"=>$fname,"lastname"=>$lname,"company"=>$company,"address"=>$address,"taxvat"=>$taxvat,"city"=>$city,"state"=>$state,"country"=>$country,"zip"=>$zip,"phone"=>$phone,"email"=>$email,"storeid"=>$storeid,"website"=>$website,"desc"=>$bdesc,"iscustcreated"=>0,"status"=>1,"createddt"=>date('Y-m-d H:i:s')); 
            $collection = Mage::getModel("inquiry/inquiry");
            $collection->setData($insertArr); 
            $collection->save();
                $first_name = Mage::getStoreConfig('inquiry/change_label/f_name');
            if($first_name){
                $first_name = Mage::getStoreConfig('inquiry/change_label/f_name');
            }else {
                $first_name = "First Name";
            }
            $last_name = Mage::getStoreConfig('inquiry/change_label/l_name'); 
            if($last_name){
                $last_name = Mage::getStoreConfig('inquiry/change_label/l_name');
            }else {
                $last_name = "Last Name";
            }
            $company_name = Mage::getStoreConfig('inquiry/change_label/company_name'); 
            if($company_name){
                $company_name = Mage::getStoreConfig('inquiry/change_label/company_name');
            }else{
                $company_name = "Last Name";
            }
            $vat_number = Mage::getStoreConfig('inquiry/change_label/vat_number');
            if($vat_number){
                $vat_number = Mage::getStoreConfig('inquiry/change_label/vat_number');
            }else{
                $vat_number = "TAX/VAT Number";
            } 
            $address_name = Mage::getStoreConfig('inquiry/change_label/address'); 
            if($address_name){
                $address_name = Mage::getStoreConfig('inquiry/change_label/address');
            }else{
                $address_name = "Address";
            } 
            $city_name = Mage::getStoreConfig('inquiry/change_label/city'); 
            if($city_name){
                $city_name = Mage::getStoreConfig('inquiry/change_label/city');
            }else{
                $city_name = "City";
            } 
            $state_name = Mage::getStoreConfig('inquiry/change_label/state'); 
            if($state_name){
                $state_name = Mage::getStoreConfig('inquiry/change_label/state');
            }else{
                $state_name = "State/Province";
            } 
            $country = Mage::getStoreConfig('inquiry/change_label/country'); 
            if($country){
                $country = Mage::getStoreConfig('inquiry/change_label/country');
            }else{
                $country = "Country";
            } 
            $postal_code = Mage::getStoreConfig('inquiry/change_label/postal_code'); 
            if($postal_code){
                $postal_code = Mage::getStoreConfig('inquiry/change_label/postal_code');
            }else{
                $postal_code = "ZIP/Postal Code";
            } 
            $contact_number = Mage::getStoreConfig('inquiry/change_label/contact_number'); 
            if($contact_number){
                $contact_number = Mage::getStoreConfig('inquiry/change_label/contact_number');
            }else{
                $contact_number = "Contact Number";
            } 
            $email_name = Mage::getStoreConfig('inquiry/change_label/email'); 
            if($email_name){
                $email_name = Mage::getStoreConfig('inquiry/change_label/email');
            }else{
                $email_name = "Email";
            } 
            $website_name = Mage::getStoreConfig('inquiry/change_label/website');
            if($website_name){
                $website_name = Mage::getStoreConfig('inquiry/change_label/website');
            }else{
                $website_name = "Website";
            } 
            $description = Mage::getStoreConfig('inquiry/change_label/description'); 
            if($description){
                $description = Mage::getStoreConfig('inquiry/change_label/description');
            }else{
                $description = "Business Description";
            } 
            $adminContent = '<table border="0">
                                <tr>
                                    <td>
                                        <table border="0">
                                            <tr>
                                                <Td>
                                                    <label><p style="Font-size:22px;"><b>Hello Administrator,</b></p></label>
                                                </Td>
                                            </tr>
                                            <tr>
                                                <Td>
                                                    <p>Mr/Ms. '.$fname.' '.$lname.' have filled dealer inquiry form and details are below.</p>
                                                </td>
                                            </tr>
                                            <tr>
                                                <td>
                                                <table border="0">
                                                        <tr>
                                                            <td><label>'.$first_name.':</label></td>
                                                            <td><label>'.$fname.'</label></td>
                                                        </tr>
                                                        <tr>
                                                            <td><label>'.$last_name.':</label></td>
                                                            <td><label>'.$lname.'</label></td>
                                                        </tr>
                                                        <tr>
                                                            <td><label>'.$company_name.':</label></td>
                                                            <td><label>'.$company.'</label></td>
                                                        </tr>
                                                        <tr>
                                                            <td><label>'.$vat_number.':</label></td>
                                                            <td><label>'.$taxvat.'</label></td>
                                                        </tr>
                                                        <tr>
                                                            <td><label>'.$address_name.':</label></td>
                                                            <td><label>'.$address.'</label></td>
                                                        </tr>
                                                        <tr>
                                                            <td><label>'.$city_name.':</label></td>
                                                            <td><label>'.$city.'</label></td>
                                                        </tr>
                                                        <tr>
                                                            <td><label>'.$state_name.':</label></td>
                                                            <td><label>'.$state.'</label></td>
                                                        </tr>
                                                        <tr>
                                                            <td><label>'.$country.':</label></td>
                                                            <td><label>'.$country1[1].'</label></td>
                                                        </tr>
                                                        <tr>
                                                            <td><label>'.$postal_code.':</label></td>
                                                            <td><label>'.$zip.'</label></td>
                                                        </tr>
                                                        <tr>
                                                            <td><label>'.$contact_number.':</label></td>
                                                            <td><label>'.$phone.'</label></td>
                                                        </tr>
                                                        <tr>
                                                            <td><label>'.$email_name.':</label></td>
                                                            <td><label>'.$email.'</label></td>
                                                        </tr>
                                                        <tr>
                                                            <td><label>'.$website_name.':</label></td>
                                                            <td><label>'.$website.'</label></td>
                                                        </tr>
                                                        <tr>
                                                            <td valign="top" width="15%"><label>'.$description.':</label></td>
                                                            <td><label>'.$bdesc.'</label></td>
                                                        </tr>
                                                        <tr>
                                                            <td colspan="2"> </td></tr>
                                                        <tr>
                                                            <td colspan="2"><label>Thank You.</label></td>
                                                        </tr>
                                                    </table>
                                                </td>
                                            </tr>
                                        </table>
                                    </td>
                                </tr>
                            </table>';
            $adminSubject = "New Dealer Inquiry from dealer";
            $adminName = Mage::getStoreConfig('trans_email/ident_general/name'); //sender name
            $adminEmail = Mage::getStoreConfig('trans_email/ident_general/email');
            $headers  .= 'MIME-Version: 1.0'."\r\n";
            $headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n";
            $headers .= 'From:'. $adminName.' <'.$adminEmail.'>';
            mail($adminEmail,$adminSubject,$adminContent,$headers);
            $email_logo = Mage::getStoreConfig('design/email/logo');
            $subject_title = Mage::getStoreConfig('inquiry/customer_email/heading');
            $email_desc = Mage::getStoreConfig('inquiry/customer_email/description');
            $email_desc = str_replace("{{Name}}",$fname.$lname,$email_desc);
            $store_name = Mage::getStoreConfig('general/store_information/name');
            $img_media =  Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_MEDIA).'email/logo/'; 
            $img_logo_final = $img_media.$email_logo;
            $default_logo =  Mage::getStoreConfig('design/header/logo_src');    
            $logo_default = Mage::getDesign()->getSkinUrl().$default_logo; 
            $email_desc = str_replace("{{Storename}}",$store_name,$email_desc);     
            if($img_logo_final == $img_media)
            {
                $logo_img = "<img src='$logo_default'/>"; 
            }
            else
            {
                $logo_img =   "<img src='$img_logo_final'/>";
            }
            $customerContent = '<table border="0">
                                    <tr>
                                        <td>
                                            <table border="0">
                                                <tr>
                                                    <Td>'.$logo_img.'</Td>
                                                </tr>
                                                <tr>
                                                    <td colspan="2"> </td></tr>
                                                <tr>
                                                    <Td><p>'.$email_desc.'. </p></Td>
                                                </tr>
                                            </table>
                                        </td>
                                    </tr>
                                </table>';
            $headers = "";
            $adminName = Mage::getStoreConfig('trans_email/ident_general/name'); //sender name
            $custSubject = $subject_title;
            $headers  .= 'MIME-Version: 1.0'."\r\n";
            $headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n";
            $headers .= 'From:'. $adminName.' <'.$adminEmail.'>';
            mail($email,$custSubject,$customerContent,$headers);
                }
                else
                {
                $message = "email_wrong";  
                Mage::getSingleton('core/session')->setSomeSessionVar($message);            
                $this->_redirectReferer();
                }
            }
            else
            {
            $message = "wrong";  
            Mage::getSingleton('core/session')->setSomeSessionVar($message);            
            $this->_redirectReferer();
            }
            }       
        }
    }
this error is displayed while calling inquiry from url eg, http://domain.com/index.php/inquiry
this was working fine before, but don't know how I got this error, now this page is not working and error is displayed whenever I open this page.
I am using this extension http://www.magentocommerce.com/magento-connect/magento-dealer-inquiry-extension.html
can anyone help me to solve this error.