I have about a dozen Visual Studio 2010 projects I\'ve been working on that are versioned in a TFS repository. Recently I went on a vacation and upgraded my computer\'s OS t
I agree with Joel - usually unbinding and rebinding fixes it.
However, if rebinding doesn't work, you might try editing the solution files directly. I have seen instances where TFS bindings are in the solution file twice and appear to be inaccurate for whatever reason - They may have the wrong number of projects and projects that are set to nothing but still listed in the solution file.
When this happens (pretty rare) I edit the files and make them the way that they should be. For example, I will delete out the 2nd set of TFS bindings (GlobalSection(TeamFoundationVersionControl) or fix any other discrepancies that I see. Then I reload the solution and that normally fixes the problem. I would definitely only use that fix as a last resort though.