I started getting this error out of the blue trying to startup VS 2010 tonight.  A quick bingle search lead me to the Microsoft Connect site where somebody has already filed it as a bug, and a quick workaround to get VS to start again was to run “devenv /resetuserdata” in the C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE directory.  The problem seems to stem from having a corrupted profile (at least it did for me), and running that command fixed the problem. 

If you are having this issue, give this a try, and head over to the Connect site and vote up the bug to get fixed.