my 4th gen 20 gig ipod is acting up again. it turns on and i can see the music and everything is fine and dandy, but when i try to play it none of the songs will play and i cant restore it. when i plug it up itunes sees it and says it needs to be restored but i get a message saying "There was a problem downloading the ipod software for the ipod "ipod". the requested resource was not found." how do i restore it?