Sprint Touch Pro won't charge/stops charging

[thebestaround]

The other day I noticed my battery low so I plugged the charger in. I came back and it was dead. When I looked into it closer, when I plug in the charger the light on the front comes on briefly, it lights up 3-4 times then cuts off. Before it died it said the battery source was "unknown" and wouldnt show an amount of life left for the battery. I cant seem to find any solution or even a similar problem. I dont think its the charger because it happens with multiple chargers. Nothing happens if plugged in through usb either. Any ideas?