My iPod 4th generation nano only works when plugged in. I have left it plugged into ac power overnight, and in the morning it shows it's complete, but when I unplug it, the screen goes dark and the device loses power. When I try to turn it on by holding the play button nothing happens, I try to reset it by holding the menu and center button for 6-30 seconds and also nothing happens. The device was used rarely from purchase and has been sitting without a charge for at least a year. I can listen to music while it's plugged in and "charging" but when I disconnect it from the ac power cord its a dead duck. If anyone can help me I'd be greatful.