Hi,
This issue comes when you have a control registered as an AsyncPostbackTrigger in multiple update panels.
Try adding the following right after the script manager declaration:
<script type="text/javascript" language="javascript">
Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler);
function EndRequestHandler(sender, args){
if (args.get_error() != undefined){
args.set_errorHandled(true);
}
}
</script>
Refer
this[
^] also.
--Amit