The version of RadEditor for MOSS is quite old. This behavior is fixed in one recent version of the control. I do not know which one though. What I suggest you to do is evaluate the latest version of RadEditor for ASP.NET AJAX and decide if you want to upgrade to the latest version of RadEditor for MOSS, which now is 5.7.2. You can check the control in the following online demo http://demos.telerik.com/aspnet-ajax/editor/examples/default/defaultcs.aspx
You can find the upgrade instructions in the following online help article http://www.telerik.com/help/aspnet-ajax/upgrade_to_a_newer_version_of_radeditor_for_moss.html
All the best,
the Telerik team
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