I am not aware of this problem and you are the first to report it. Are you able to reproduce it in the ContentAreaMode="Div" live demo and under which browser?
I also attached my test project. Is the problem reproducible in it? If so please provide reproductions steps along with video or screenshots. If not, modify the project so that it starts to demonstrates the issue and send it back for examination along with steps.
All the best,
Rumen
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 now.