I tested the scenario that you describe but I can not get the appearance on the provided image. Please take a look at the attached page and let me know if I am missing something. In case this does not help I would suggest that you open a support ticket and send us simple runnable project where we can observe the issue and come back to you with a suitable solution.
All the best,
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!