This will likely be caused by some global CSS setting that you set for DIV or SPAN elements, e,g,
Or something similar.
My suggestion would be to switch off any global custom CSS that you use and see whether this fixes things.
If you are unable to determine or workaround the problem, please send us a small working application in a support ticket. We will examine it, determine what is causing the issue, fix it and send it back to you.
the Telerik team
Check out Telerik Trainer
, the state of the art learning tool for Telerik products.