This is kind of a general issue for a lot of different problems I've had when working with RadGrids. If there's some sort of error in the code, I've been having a difficult time (in many cases) trying to figure out what exactly the problem is. In particular, if some sort of error is introduced that affects the edit/insert mode, my only sign that something is wrong is that the edit/insert buttons stop working and the Firefox error console reports something like the following:
Is there any way to get more specific errors for RadGrid postbacks? Is there some logging that I'm not aware of that might help to isolate the issue? I'm usually reduced to guessing at this point until I manage to hit whatever the problem is.