I think (from memory) that the 'original profile' folder users.user will now be almost empty, apart from the nuisance ZUNE files.
If you log in with the original login, you will pickup the user.000 profile, as that original user now points to that profile folder. MS assured me that I could continue to run with that . . . but I don't trust what MS level 1 technicians tell you, so I did manage to roll back.
I theory, if your problem was associated with an upgrade (as it was) MS should help you sort it out . . . .if you trust them more than you trust expertise and experience on these forums (fora??).
Tyler - is the Rollback option not now available under 'System/Updates'?