Hello Jeff Mah,
I apologize for the late response.
I have just talked with our RadControls team, and it turned out that this is a known issue. The fix for this will most probably come with 2009 Q1 version of the controls. We will release a Service Pack of Sitefinity which will include those contols right after the Q1 release.
Currently you can fix the problem by copying the EditorDialogs folder from the RadControls for ASP.NET
AJAX installation to the root of your application and setting the
<telerik:radeditor id="RadEditor1" ExternalDialogsPath="~/EditorDialogs" runat="server"></telerik:radeditor>
After that open the \EditorDialogs\TableDesign.ascx file and put
in the style attribute of the following line:
<div id="TableDesign_PreviewTableHolder" style="margin: 0;"><!-- / --></div>
<div id="TableDesign_PreviewTableHolder" style="margin: 0;height:350px;overflow:auto;"><!-- / --></div>
We apologize for the inconvenience.
the Telerik team