Hmm, I wonder if doing so made HIS songs the ones your computer is allowed to play. I don't know what happens if people with different accounts sync at the same computer. I thought the worst that could happen is that the songs that were on his ipod would be replaced with your library, but I have no means to try this out to see what happens. All I can think is that it is a permissions issue, but like I said, I really have no clue.