I just had this problem after doing a battery test. It was hooked up to the computer for at least an hour in the cycle from low battery warning to apple logo.
I decided to unplug the iPod from my computer and plug it into the wall charger. When I unplugged from the computer (it had the apple logo only - not Do Not Disconnect) it came on to the main menu, so I tried plugging it back into the computer. iTunes recognized it right away and it's now syncing.