What a drag. Increasingly my VS 2008 has begun issuing this error when I open a trustry old project from TFS and start working on it.
There are a couple of links for it on Google, and the solution that helped in my case is this:
1) Go to "c:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE\"
2) Run the command devenv /resetskippkgs
Perhaps I’ve overloaded my VS with add-ons, plugins, uninstalls and what have you not. Anyway, today is VS 2010 RTM day so anytime soon now I’ll have a shiny new VS install where a lot of the stuff will be built in.