Have you upgraded from a previous version of the control? If this is so, can you please check if you have set the ToolsFile property to point to a non-existing file - this could be the reason for such behavior. Make sure that the path points to the exact location of the ToolsFile.xml.
e.g. if your physical path of the RadEditor's ToolsFile.xml is
C:\Program Files\Common Files\Microsoft Shared\web server extensions\wpresources\RadEditorSharePoint\184.108.40.206__1f131a624888eeed\RadControls\Editor\ToolsFile.xml
Your ToolsFile property must point to "/_wpresources/RadEditorSharePoint/220.127.116.11__1f131a624888eeed/RadControls/Editor/ToolsFile.xml"
Please note that the name of the folder 18.104.22.168__1f131a624888eeed
is unique and is built like this:
/<control's version>_<Unique Token>/
the Telerik team