Hi,
I have the same issue.
I used to add the new template column into the grid , after that , the client select column does not seems to work for first click.
The issue only comes with the rad window , when I used to run the page with browser (not a pop rad window) I am not able to find the errror.
When I used to run the page in rad window and clicked for first time , I am getting a javascript error "TypeError: e is null" in ScriptResource.axd.
Please let me if you find a solution for it.