The observed errors indicate that there are script issues in the application. You can check out the following topic for possible reasons:
I have prepared a sample RadGrid web site to test the described behavior. Can you please run the attached application and let me know if it works as expected on your side, too?
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 the blog feed