I am afraid, we have not been reported similar issues so far. It is possible to be connected with caching. Could you please specify if you are using Session or ViewState persister on the problematic page? It would be very helpful if you can isolate the problem in a sample project and send it to us. I would also need to know the server and .NET version where you project is hosted as well as the browser you use to surf 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