My ipod (160gb classic) has developed an annoying new trick. When playing tracks, be it playlists, shuffle or otherwise, it will play a few songs without any problems then for some reason will be unable to play the next one (or find the artwork which I know is on there) and skip onto the next track. It won't be able to play this one either and so will keep skipping tracks until I stop it and go back to the main menu and start a new shuffle. Obviously after a few songs the problem will start again. Sometimes it will play approx 100 songs before it starts skipping, other times it might be 10 successfully played songs. Any ideas/suggestions?