Guys,
Maybe this will sort some things out. Here is what I have done to solve my problem. In your page, add the following javascript code snippet in the head tag:
Code:
<script type="text/javascript">
/*
* Redirect to login page when a DWR request is send after a session timeout
*/
try {
if (dwr && dwr.engine) {
dwr.engine.setTextHtmlHandler(function() {
document.location = 'here goes the url to your login page';
});
}
catch(err) {} //ignore
</script>
Make sure you also have the dwr libs on each page included 
If you make use of the SiteMesh decorator, you can place this code snippet in the decorator so you won't have to copy it on each page