The add-in that Visual Studio is trying to load is actually the Visual Studio 2010 add-in, it is only misleading that it is stored in the 2005 directory. Can you tell us which version of Widows are you using for your tests. Our add-in has been tested under Windows 7 and Visual Studio 2010 and there have been no problems yet. Can you tell us more about your configuration so we are able to test in that environment and see whether we meet similar behavior?
the Telerik team