Same is happening with me. If you have 2 chargers use the other one for a while. After a while that one will start saying the same thing. I was looking at my worse charger and I saw that the side was chipped. That may be the problem.
your data cable might be corrupted
The battery is shot. Try charging it (without using it) for at least 4 hours, if the problem persists it will likely require a replacement.
Repair the problem with the charging system causing the light to come on.Repair the problem with the charging system causing the light to come on.
Have the charging system checked. The light comes on when there is a charging system problem. it may be a battery, alternator or a battery problem.
Plugged fuel or air filter? Plugged catalytic converter?
storing of energy
if you are plugging it into your cp, it might be blocking your ipod charger usage, or if you plugged it into the wall, then you might have to turn on a light switch to actually make it charge, or if you plugged it into a multi-outlet-extender-thingy, then you might just have to turn the multi-outlet-extender-thingy on, and if none of that works, there might be a problem with the charger. hope i could help.
It is a hardware problem--check that it is plugged in!
alternator needs to be replaced. battery also might be a problem due to the alternator not charging it
Problem with the charging system.
Take your iPad the Apple Store, They may be a Problem with the 30pin Connecter on your iPad.
its trying to resolve a problem