This is very strange. Could you please send us your EditorToolsFile.xml?
Could you also elaborate if you have performed projects upgrades recently? The RadControls are changing with each version and there might be something related to an upgrade.
We will inspect the file and see if it is causing a problem with the last official release with Sitefinity.
the Telerik team
Check out Telerik Trainer
, the state of the art learning tool for Telerik products.