Recharge it or run it from the AC adapter. There is a reset button - look for the little hole on the bottom (near the docking connector and power connector). Take a straightened paperclip and insert it into the hole. It will go in a surprisingly long way, but it will hit the reset button inside the player.

Did you notice any other problems? Hard drive noises / clicking? Sounds? Also, what version of the firmware do you have on the player - had you upgraded to the most recent version?