I am not aware of this problem. Are you able to reproduce it in the Default Example
of RadEditor, which runs the latest version of the control? If yes, could you please provide detailed steps which reproduces the issue as well as a screenshot demonstrating it?
If the problem is not reproducible in the live demo, upgrade to Q1 2011. If the problem still persists, open a support ticket and send a simple working project that demonstrates it. We will examine it and provide a solution.
the Telerik team