I have a user control defined as:
<div>
    <asp:TextBox ID="txtBox" runat="server"></asp:TextBox>
    <asp:CustomValidator ID="validator" runat="server" ControlToValidate="txtBox"></asp:CustomValidator>
</div>
<script type="text/javascript">
    $(document).ready(function () {
        $('#<%= txtBox.ClientID %>').blur(function (event) {
            $('#<%= txtBox.ClientID %>').removeClass('errorTextBoxServer');
            testBox($('#<%= txtBox.ClientID %>'), <%= RegularExpression %>);
        });
        testBox($('#<%= txtBox.ClientID %>'), <%= RegularExpression %>);
    });
    function <%= txtBox.ClientID %>_validateBox(source, args)
    {
        $('#<%= txtBox.ClientID %>').removeClass('errorTextBoxServer');
        args.IsValid = testBox($('#<%= txtBox.ClientID %>'), <%= RegularExpression %>);
    }
</script>
testBox is defined as:
function testBox(thisBox, RegularExpression) {
    if ($(thisBox).val() != "") {
        var regex = new RegExp(RegularExpression);
        var value = $(thisBox).val();
        if (!regex.test(value)) {
            //event.preventDefault();
            $(thisBox).addClass('errorTextBox');
            return false;
        }
        else {
            $(thisBox).removeClass('errorTextBox');
            return true;
        }
    }
    else {
        $(thisBox).removeClass('errorTextBox');
        return true;
    }
}
And it is placed in a web page as follows:
<asp:TextBox ID="txtD1DOB" runat="server" readonly="true"></asp:TextBox>
<wpm:ValidatedTextBox id="txtUpdatedBalance" runat="server" RegularExpression="/^\d{1,3}(,?\d{3})*(\.\d{2,4})?$/" />
Using the following js:
$(document).ready(function () {
    var $j = jQuery.noConflict();
    $j("input[id*='txtD1DOB']").datepicker({
        changeMonth: true,
        changeYear: true,
        dateFormat: "dd/mm/yy",
    });
});
When I run the app js throws the error:
Object doesn't support property or method 'datepicker'
If I remove the user control <wpm:ValidatedTextBox id="txtUpdatedBalance" runat="server" RegularExpression="/^\d{1,3}(,?\d{3})*(\.\d{2,4})?$/" /> then the datepicker works as expected.
I have checked if there are other versions of jquery-ui loading but can't find anything and can't seem to find what would be causing the issue. Any ideas?
EDIT: I tried changing the user control to simply:
<asp:TextBox ID="txtUpdatedBalance" runat="server"></asp:TextBox>
<asp:RegularExpressionValidator ID="txtUpdatedBalance_RegularExpressionValidator" runat="server" ErrorMessage="Invalid value" ControlToValidate="txtUpdatedBalance" ValidationExpression="/^\d{1,3}(,?\d{3})*(\.\d{2,4})?$/"></asp:RegularExpressionValidator>
But the same thing occurs. Removing the RegularExpressionValidator allows everything to work.
EDIT 2: In response to Frebin Francis in the comments the entire head section is:
<head runat="server">
    <meta charset="utf-8" />
    <title><%: Page.Title %> - My ASP.NET Application</title>
    <asp:PlaceHolder runat="server">     
          <%: Scripts.Render("~/bundles/modernizr") %>
    </asp:PlaceHolder>  
    <webopt:BundleReference runat="server" Path="~/Content/css" /> 
    <link href="~/favicon.ico" rel="shortcut icon" type="image/x-icon" />
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
    <link rel="stylesheet" href="https://ajax.googleapis.com/ajax/libs/jqueryui/1.11.3/themes/smoothness/jquery-ui.css" />
     <script src="https://ajax.googleapis.com/ajax/libs/jqueryui/1.11.3/jquery-ui.min.js"></script>
    <script src="Scripts/wpm_portal.js"></script>
    <meta name="viewport" content="width=device-width" />
    <asp:ContentPlaceHolder runat="server" ID="HeadContent" />
</head>
It also has a ScriptManager defined as:
<asp:ScriptManager runat="server">
    <Scripts>
        <asp:ScriptReference Name="MsAjaxBundle" />
        <asp:ScriptReference Name="WebForms.js" Assembly="System.Web" Path="~/Scripts/WebForms/WebForms.js" />
        <asp:ScriptReference Name="WebUIValidation.js" Assembly="System.Web" Path="~/Scripts/WebForms/WebUIValidation.js" />
        <asp:ScriptReference Name="MenuStandards.js" Assembly="System.Web" Path="~/Scripts/WebForms/MenuStandards.js" />
        <asp:ScriptReference Name="GridView.js" Assembly="System.Web" Path="~/Scripts/WebForms/GridView.js" />
        <asp:ScriptReference Name="DetailsView.js" Assembly="System.Web" Path="~/Scripts/WebForms/DetailsView.js" />
        <asp:ScriptReference Name="TreeView.js" Assembly="System.Web" Path="~/Scripts/WebForms/TreeView.js" />
        <asp:ScriptReference Name="WebParts.js" Assembly="System.Web" Path="~/Scripts/WebForms/WebParts.js" />
        <asp:ScriptReference Name="Focus.js" Assembly="System.Web" Path="~/Scripts/WebForms/Focus.js" />
        <asp:ScriptReference Name="WebFormsBundle" />
    </Scripts>
</asp:ScriptManager>