I've a PC and Mac Mini, so I buy my music on the PC and then transfer to the Mac Mini. I've got the firewall turned on and I only use one account for iTunes. Keep my that I already authorize the Mac mini with same account info in the PC. To make it short I had transferred a couple of songs to the Mac mini which I just purchased on the PC. Then I tried updating my iPod which told me some songs weren't authorize but they have the same account info...What gives??