When I left my mp3 on till the battery went dead, the same problem happened for me.
Usually Li-ion batteries inside of the mp3's have a high reviving voltage so charging it with the USB from the computer only gives you 1 to 3 volt at the very least amperage.
Sooo.... this is how I fixed my mp3
1. take off the squews of you mp3 to expose the inside case
2. there should be a battery (mines black rectangualar)
3. there should be two main wires running from the battery to the curcit board.
4.find the two weld point for these two wires and attach two different wires to the weld point.
5.make sure that the wires are insulated from each other and carfully place them outside of the mp3.
6. squew back on the mp3.
7.hook up two to three 1.5 AA volt batteries to the right terminals of the wires you have attached.
8. if you read the voltage capacity of your mp3's Li-ion it should say 3 voltage but if it is higher, make sure that you put a voltage 1+ higher to the wires that you have attached
9. this should give the mp3's Li-ion enough juice for it to start up and be charged with a computer.
(WARNING) Do Not Apply Voltages +2 Higher then the Li-Ion battery itself.
Make sure that you are carful when you are doing this. And here is the picture of my mp3 going under that process.
