I have the same issue, I cant sync because it says I am not Authorized. I log my ID out of iTunes, I log back in, I Authorize both iTunes accounts and it goes around again. I cant de auth all computers because I have already done that in the last 12 months, not that I think that will solve the issue.
There is a by-pass to this. Instead of syncing just make some changes in photos or music or tones - and press apply. That's it iTunes will sync normally. Just don't press sync.
I have the same problem. It must be related to Ios7.