Some other remarks:
I normally avoid (and warn people to stay away from) the System Restore stuff in Windows except as a very last resort -- I just don't trust it not to result in having some things restored to one version, and other files out of sync.
So I almost *ALWAYS* do a full system restore when I have a mystery situtation like this.
I may still do a full system restore -- but in this case it seemed like restoring just the User Profile to a point 2 days ago was pretty harmless, at least as a first try.
I may go back and try to figure out which file(s) got corrupted, if i can figure out how, using some file comparison tools.
Fyi here is my general recovery procedure when i encounter serious problems like this:
First, make sure you don't make situation WORSE, by making a full image of the BAD CORRUPT drive, if at all possible. Put this someplace safe.
Second, if I am going to do a system restore from drive image / backup, do so on a NEW hd -- if you don't have a new hd you can use as your new hard drive, buy one. If the restore is successful, this will be your new hd drive, and the suspicious one can go on the shelf marked as an untrustworthy backup.