iPad Battery will not charge?

I charged my iPad 1st Gen Wi-Fi + 3G last night. The charge on it last night was at 81% before I shut it off for the night and hooked it up to the charger. I wake up this morning and turn it on and batter icon with the lightning bolt showing it's charging shows up. It's that screen when your iPad is not charged up enough to power up. It has been showing this screen for roughly 6 hours now and I still get the same screen. I can tell that the iPad is detecting the charger because, when I take it out, the icon to show that you need to put in the charger shows up. I put it back in and the lightning bolt shows up again. I don't know what to do. HALP! (And yes, the software has been updated to iOS 5.0.1)