iPad no longer recognizes USB cable - charging problem, won't appear in iTunes

Hi all,

A bizarre problem popped up with my iPad 2 a couple of days ago. After having used it fine for over 2 years, all of a sudden it is no longer recognizing when I plug the cable into it. I tried 3 separate cable attached to wall chargers, and each time, the iPad does not recognize that there is a cable plugged in (usually it vibrates briefly and chimes to indicate it is charging). The battery icon does not show that it is being charged.

I left it plugged into the wall overnight, and it went from 5% to 22%. So weird! So in effect it's charging VERY SLOWLY, but the iPad doesn't even seem to know it's supposed to be charging.

I figured a restore was in order but when I plug it into my computer, iPad is not showing up in iTunes. Obviously the iPad is not understandsing that it is connected since again, I get not chime/vibrate when I plug in, and the battery icon does not show the charging indicator.

Anyone else have this bizarre problem? Anything I can do? I recently upgraded to iOS 7, if that's any help.

Thanks!