bsiu99 here's what I had to do to get sync to work. Not sure if EVERYthing was part of the fix or just some of it.
On the phone:
1. disabled wifi
2. disabled cellular
3. turned off iCloud backup
In iTunes:
1. disable ALL syncs you can, music, pictures, TV, movies, etc, the only one I don't find a way to stop is apps, sync from phone summary page (or apply changes, I can't remember which button shows up at this point, it was late and I was tired).
2. eject phone, sync actually stopped on the phone when I did this, to my surprise!
3. close iTunes.
4. reboot phone
4a. you can reboot your computer if you like, but I did not do this, so I don't know if it's necessary.
5. open iTunes
6. connect phone via usb
7. on "tones" page, select sync individual ringtone, sync.
8. select sync of next ringtone, leaving all previous checked, sync.
9. repeat 8 until all your ringtones are synced
10. on "music" page, select individual play list (if that is what you want/need, otherwise make your selection by album or artist, etc), sync.
11. repeat step 10 for each playlist (artist, album, or which ever) leaving all previous selections checked, sync.
This was the ONLY way I have EVER gotten my iPhone 5 to complete a sync. I've had the thing for over a year now and wow, am I shocked and surprised. Anyway, it may work for you this way as well. It's just a lot of trial and error.
