Sometimes I will notice the audio is out of sync on my iTunes store bought videos. Rebooting the computer helps until the next time. This really started to become a problem over the last few months. This is a 15" MBP, 2009 bought in March, 4GB ram. Storage is on a 1TB WD drive in a LaCie 2 big tripple enclosure with firewire. No extra software installed and the computer is only used for iTunes and internet. Has all updates. Any ideas?