Are you using the updated Google Analytics tracking code in your header?
Should look like this:
<script>
(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
})(window,document,'script','//www.google-analytics.com/analytics.js','ga');
ga('create', 'UA-XXXXXXXX-X', 'auto');
ga('send', 'pageview');
</script>
Use the new format for tracking events:
onclick="ga('send', 'event', 'Category', 'Action')"
The send and event values you can't change, without them the script won't send anything to Google Analytics. The Catergoy and Action values are required, you can give them any name you want. For Action I would recommend click, that's the action you're registering with onclick. You can even add more optional parameters if you need to.
Your code could look something like this:
<form action="http://webshop-cs.tecdoc.net/sonnak/?user=sonnakno&pass=sonnakno&articleCountry=NO" method="post" target="_blank">
<input id="submit" src="http://www.sonnak.com/wp/wp-content/uploads/2010/07/lv2.jpg" type="image" value="submit" onclick="ga('send', 'event', 'Form', 'click')";"/>
</form>