In Q3 2011 we have moved all skins in an external assembly for various reasons. We are aware of an issue with the Upgrade Wizard of the Telerik WebUI VSExtensions, that the Skins assembly is not copied properly with the rest of the dlls.
Please find more detailed information on the subject in the following sticky forum thread:
Separate Skin Assembly in RadControls for ASP.NET AJAX with Q3 2011
the Telerik team
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