yeah tried it on 2, and tried normal batteries on both of them as well, both charge fine. I don't uinderstand it, I left the battery out of the way, it hasn't been touched since I last used it.
If nothing else, you might just try plugging it in and just let it be and see if it will eventually take a charge. Could be that its just stone cold our of juice and needs a little time. Although I suspect you'll be shopping for a new pandora compatible battery soon.