The main difference between the Lite and the Full version of RadEditor for MOSS is that the Lite is based on the classic ASP.NET RadEditor and the Full is based on the ASP.NET AJAX version of the control. You can not see the issue in the Telerik demo site, because in all the examples we are using the latest RadEditor for ASP.NET AJAX.
Unfortunately we upgrade the Lite version of RadEditor for MOSS in rare cases. For example, if a new version of a major browsers, such as IE8, is released.
What you can do is try using the trial version of RadEditor for MOSS 5.6.0. Here are the upgrade instructions Upgrade Instructions from version 4.x to version 5.x
. Then, if you are pleased with the Full version of the control you can purchase the Latest Telerik ASP.NET AJAX controls.
the Telerik team