Q: I rented some videos from iTunes and tried to sync to my iPod touch. However, I’m not getting error 5103 when I try to do this. I have done this many times before and it has worked without any problems. Everything else also seems to be working fine. Can you help?
A: The usual cause of this problem is that iTunes cannot authenticate your rentals against the iTunes Store. Unlike normal purchased content, iTunes must update your authorization keys whenever you transfer a rented movie from iTunes to another device or back again. This means that you must not only be connected to the Internet when you attempt to transfer a rented item, but must be actually logged in to the iTunes Store with the account that was used to rent the item in question.
Check your iTunes Store page and ensure that you are logged in with the correct iTunes Store account, and ensure that your Internet connection is up and working properly.