In order to help you further I will need some additional information. Send me the web.config file of your SP2010 site and the configuration files of RadEditor for SP2010. These are ConfigFile.xml, ListConfigFile.xml, ToolsFile.xml, ListToolsFile.xml and SPEditorTools.js, which are in the /Program Files/Common Files/Microsoft Shared/web server extensions/wpresources/RadEditorSharePoint/6.x.x.0__1f131a624888eeed/Resources/ folder. I will use the files to reproduce the problem on our test server and advice you furhter.
All the best,
the Telerik team