Thank you for contacting us.
Are you using Q1 2011 SP1 version? The issue in question is not present in the latest versions of RadControls if your combo-box column is set up correctly.
If you still experience any issues, I would like to kindly ask you to open an new support ticket and send us a small sample project, which demonstrates your scenario. This will allow to investigate your particular case and provide you with accurate assistance.
the Telerik team
Register for the Q2 2011 What's New Webinar Week. Mark your calendar for the week starting July 18th and book your seat for a walk through of all the exciting stuff we will ship with the new release!