Could you please elaborate on your scenario a bit? What is especially done in the AjaxManager AjaxRequest event handler after the ajax request is invoked for instance, and does it makes any difference if you comment the code there out?
Sending a sample project illustrating your setup and the described problem, could be of great help in finding out the source of it. Or providing the page in question might be useful as well.
Looking forward your reply,
the Telerik team