Is it actually charging, does it run from your power pack while its charging (ie on mains), are you using a separate mains plug transformer or charging it from usb - and is there a reset pin-hole ?
I have a Sony eReader and its always a bit of a faff getting it back to serviceable when you let it completely discharge the battery, I've found that a reset followed by a long charge usually brings it back to life, and I bought a proper charger rather than use the usb connection.