CollapsiblePanelExtender and Null error

We are using CollasiblePanelExtender Ajax control.  When opening and closing panel it makes a call to server and puts a value in Session.  After about the second click we see this error "AjaxControlToolkit.ControlBase.onsubmitCollection.length is null or not an object."........also error appears spradically when updating.........users say they can update data a field box at a time and then hit update button with no error.........

Also this only happens on our Prod box and no other environment.....Its a Intranet site with a small user base of 50-100 users.......

Any help with direction of how to troubleshoot this problem would be appreciated.

thanks