Hi James,
Do you by any chnace have .NET Framework 2.0 Beta, or Visual Studio 2005 Beta installed on your pc. They might be causing the problem. Also see the following MSDN link that talks about this error.
http://lab.msdn.microsoft.com/productfeedback/viewfeedback.aspx?feedbackid=bab82d4a-62c8-484a-a0aa-149646076b18
Ankita