I suggest you to upgrade to the latest version of RadEditor for MOSS, which now is 5.4.1.
Here are some of the enchantments in this version
1. RadEditor updated to version 2009.1.530
2. Fixed a problem with setting the spell dictionary path from the editor configuration path
3. If MOSS table CSS layouts file is not loaded, the editor will use internal table layouts in the table dialog.
4. Added a fix for updating reusable content in WCM editor fields (developed by Rich Finn).
5. Updated the SharePoint content provider for the editor file browser dialogs. Fixed some broken file operations.
Regarding the skins problem you should know that there is no longer Default2006 skin. It is transformed to Default. Also you can find the available skins if you open the Program Files\Common Files\Microsoft Shared\web server extensions\wpresources\RadEditorSharePoint\5.x.x.x__1f131a624888eeed\Resources\ToolImages
folder. There you can find RadEditorStyles_[skin name].css files (for example RadEditorStyles_Default.css).
I hope this helps.
the Telerik team