iTunes 10.5 hangs during iPhone 4 sync

Just installed iTunes 10.5 and attempted to sync iPhone 4/4.3.5 several times. The process hangs while "Backing up" with the status bar right under the t in (Step 1 of 5). I've swiped the phone to cancel, which leaves iTunes continuing on as if the phone were still syncing. I used Task Manager to quit iTunes on Win Vista, restarted iTunes and attempted to sync again. Hangs in the same place. So, I restarted the computer, restarted iTunes and it's still hanging during Backing up... I am so frustrated! Help!!!