Can't sync with ipod touch

Question

I had to delete my FF Sync account because it would no longer sync with my ipod touch no matter what I did, so I gave up. I cannot set up a new sync account because it says my email is already in use. Need assistance.

Answer 1

OK, I wound up going to my local Genius Bar, and here's what we did:
1) reinstalled iTunes ...still didn't sync
2) repaired disk permissions...same thing
3) created a new user account on my MacBook and checked to see if my iPod touch would sync then...it did
4) went back to my user account, re-restored my iPod Touch and deleted the iPod backup file...and then it synced. At this point, it looked like it was a corrupted backup file.
When I got home and hooked it up to let it finish syncing, I realized that none of my photos had been transferred to my iPod touch, so I told it to...and the -50 error came up again. Another round of restoring the iPod and deleting the backup file, then I told it to load my photos from the My Pictures folder, rather than from iPhoto (which was the original setting before all this happened)...and it was fine. So my guess is that something in iPhoto 6 is tripping up the iTunes software (or vice versa) and screwing up the backup/sync process. I'll continue to keep an eye on it and see if that holds.
Thanks to Ariel at the Genius Bar in the Apple Store at the Menlo Park Mall, Edison, NJ! You were a great help, and thanks for your patience!