I was trying to use FxCop 3.5 to make up for some of the missing features in the current version of Team System Code Analysis.  Specifically, the spell checker.

I ran FxCop on my (fairly) clean development machine running Vista, Office 2007 and Visual Studio 2005 Team Suite SP1.

Everything ran, but it found no spelling errors even when I purposely put them in to confirm that spelling was being checked.

The solution? Install Office 2003 Proofing Tools - available on MSDN Subscriber Downloads.  Evidently the API changed significantly between 2003 and 2007.  The next version of FxCop will ship with its own non-Office-dependent spell checker and this fix won't be required.