Suddenly my iPod will not play any of the music I've downloaded from the iTunes store. It will skip right over those tracks. If I force it on an iTunes track it will sit at 0:00 the entire time. It plays the tracks from my CD collection just fine. Any sugesstions? I have over 200 songs from the iTunes store so this is a big deal. Oh, and I have a 4th gen, click wheel non-color iPod.