I have inspected the issue but it can not be reproduced in any of our on-line demos. Would you please test with the latest version of our controls and let us know if the issue is still observed?
You can also check this blog post in case the issue is invoked by this CSS IE limitation.
Hope this will be helpful.
All the best,
the Telerik team
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 their blog feed