I had the similar problem. I couldn't sync my musics because itunes need to sync my apps first but it shows 'the iPhone could not be synced because this computer is no longer authorised for purchased items that are on this iPhone'. So the sync stops. I authorised to my computer, but it doesn't work.
Finally I found this problem caused by my apple account. I changed the reigion of my account from country A to country B recently. I used the same account ID but registed in country B to authorised my computer but the apps are bought with the same ID but registed in country A. So the problem comes.
To solve it, I chaged my ID registed reigion back to country A and deleted 'C:\ProgramData\Apple Computer\iTunes\SC Info' folder (hiden folder). After that, authorised my computer again. Then I can sync my apps and music.
Hope this help a little bit.
Enki: someone else previously (you, maybe?) suggested changing the region back, and I thought that perhaps it might work for me. I had a go, but it is a bit of a rigmarole, involving entering a new credit card and an address in the previous region. I found that I simply wasn't able to do that: I could edit the credit card but not the address. User-friendly is not the way I would describe the Apple store!
Now I still get the endless "authorise - already authorised" loop, but most of the apps work and can be synced, despite what the pop-up box says. I expect I'll find what ISN'T working shortly, and then I'll be back here looking for a proper solution.
Thanks for the suggestion, though.
Solved this problem....
I am using iphone 4 on ios 7 on Windows OS Dell Laptop 1534
De-authorize my Apple ID
Log out of my Apple ID both on laptop and on mobile as well
restarted my system and turn off my iphone and turn on my iphone as well
Re-login on laptop and mobile, Authorize my PC for sync
I had this Problem, But i resolved,
I think this happens when we purchase in more than one computers with same AppleID in iTunes,
Delete the apps from your iPhone which you purchased via secondary computer,
And Try Syncing your iPhone in your Primary computer, it should sync without any warning..
This solved my problem, I didn't red the discussion fully, sorry if i repeated somebody's reply..
I am using the following :
iTunes 11.1.3 in Primay Computer,
iTunes 11.1.1 in Secondary Computer
If this solved your problem, please comeback and let others know..
I don't have a second computer, I only ever had 1 ID except when I had to switch to iCLOUD and change my username to an email.....then problems began.
Can't log in with my old login as it's gone since I was FORCED to change to use iCloud.
This is an apple problem we shouldn't be dealing with and months later as it's still unrseolved.
I might imagine deleting all my apps and re downloading them might work but this is an extreme hassle as I have dozens of paid apps and will I'll loose all my preferences, ie like with my GPS all my input locations will be deleted...and no guarauntee it will even work.
I shouldn't have to do this and not even be sure it will work when Apple should just FIX IT!
Dear Apple, if you please with this statement
the iPhone could not be synced because this computer is no longer authorised for purchased items that are on this iPhone
will show us the list of apps which isn't authorized on our computers (instead of this bug in law http://support.apple.com/kb/TS1389) it will save all of us from millions hours of idiotism.
Thank you in advance from all of your customers.
Click on your iPad/iPhone name in Devices.
Click Back Up Now.
If there are purchases that need transferring click Transfer Purchases.
When there are problems with tranferring purchases it will give you a list of apps which aren't authorized on the computer.
Less obvious then it should be and still very annoying.
It was a cryptic situation for me with the error message from Apple being less than helpful. After 8 hours of fooling around with this issue I just gave up and reset the phone to factory settings and started adding stuff back in. That worked. Why hasn't some newspaper written the story. "50 billion dollars of user time wasted by Apple customers trying to get their iphones to work"