In a summary, what I can suggest is:
- confirm the handlers are present and are attached in the main page, not in the content page
- try removing the AjaxControlToolki assembly if present (even from the bin, not only as a reference)
- try adding a static handler in the markup, if possible for your scenario. In case it is needed only conditionally you can add a flag to check for in its beginning and return; if it is not satisfied
If none of this helps I advise that you open a support ticket and send us a simple, runnable project
we can use to reproduce this behavior in order to investigate it.
the Telerik team
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the RadControls for ASP.NET AJAX, subscribe to their blog feed