Iv had this problem since I first downloaded iTunes 8. When I try to play a song purchased off of the iTunes store I get a message saying i need to authorize my computer. Though once i do that it says that my computer is already authorized and the song still won't play (with the exception of a few songs). I found it weird because a week ago the songs randomly started working on my iPod touch when they previously didn't), though i restored it the other day and now im back to where i started. Yes, i purchase all my music on the same account. Yes, iv tried deauthorizing and reauthorizing my account. Which btw i have a weird problem when it deauthorizes as well. When I deauthorized my account, the few songs that did work still played and didn't require me to authorize my account. HELP!!!