Can't sync new iPhone 4 with iTunes without it locking up iTunes

Question

Got my new iPhone 4 last Friday. They tell me I need to register it and sync it. Didn't get around to trying that until yesterday. Tried most of the day and night last night, using iTunes 9.whatever it was. Kept on locking up iTunes. Tried deleting iTunes, reinstalling it and trying again. Didn't work. Even trying to register the phone made iTunes lock up.
Downloaded iTunes 10 last night. Have the same situation, BUT, it finally did allow me to finally register my phone this afternoon. Thought the problem was solved. Still won't allow me to sync.
Sync starts up (took it off the auto-sync setting) and it says it is going to backup the device - Step 1. Sometimes the progress bar moves 1/4 inch, sometimes 1/2 inch. Sometimes it just has the moving pattern on it. Once or twice, it actually got to Step 2, whatever that is. It always locks up. I've left it running for hours... still won't work.
Was told to delete iTunes, restart, delete trash and reinstall it. Tried that SEVERAL times, still didn't work. Was told to delete some other files (the IT guy was standing beside me because I have NO clue as to what to do with these files) - at least 1 file from the Library and not certain where the others were. That didn't work either. It just keeps on locking up iTunes and quite often, when I check with Force Quit, it shows that iTunes isn't responding. I repaired disk permissions. Didn't work. I unchecked what to sync - just trying to sync Apps now, and it still doesn't work.
All software is up-to-date on both the phone as well as my MBP. I'm at a loss. Anyone have any ideas?
Just tried it again and just plugging in the iPhone caused the beach ball to start spinning. I've GOT to be doing something wrong, but I'm at a loss.
Thanks in advance for your help.

Answer 1

After purchasing a new iPhone 5S I had a problem syncing iTunes with the iPhone...At the Apple Store, the Service Rep backed up my iPhone to iCloud in order to transfer all data from the old phone to the new phone. At home when I tried to sync iTunes with my new iPhone 5S, iTunes would not recognize my new phone. I discovered iTunes was configured to back up data to my Mac hard drive and the iPhone was configured to back up data to iCloud. There was a conflict, subsequently causing iTunes to not recognize my new iPhone 5S. My solution was to delete iCloud from the iPhone. After doing this, iTunes synced with the iPhone with no problems. No data was lost and syncing occurred normally.
I recommend these as possible solutions:
1) The Apple store will back up your phone using iCloud. Make sure that iTunes is configured to back up to iCloud before you plug your new phone into iTunes for syncing/back-up. If your iTunes is configured to back up data to your hard drive, ensure that the Apple Store does not back up your phone data to iCloud. You will have to back up all iPhone data yourself at home on iTunes.
2) If they insist on backing up your phone data to iCloud from your old phone to your new phone then, be sure to delete the iCloud account off your new phone before you try to sync your new phone to iTunes.
I used the 2nd solution to solve my syncing issues. Everything works great now. iTunes recognized my new phone and can now sync/back-up data with out problems, error messages or loss of data.
Hope this helps everyone out! I intend to get drunk to relieve all the stress and hopefully restore my sanity as a result of having to solve this problem while having to act as my own Apple support staff!