I have an iPod 80gb 5th gen that has messed up on me. When I plug it via the USB it makes a grinding like noise for about 6-8 seconds, and displays a sad face with www.apple.com/support/ipod. It shuts off and then displays please wait very low battery. About 30-45 seconds later it will turn on a making the grinding noise for about 6-8 seconds again. What can i do?