I get this sometimes when charging from the battery charger I got. I even use the default USB chord that came with it, but it will sometimes freeze. I don't understand it and am a little worried it means something bad is happening but it doesn't seem to damage anything. I would also love to know if anyone has any idea of actually why this happens.
I've seen this same symptom. I thought it was a runaway process or something. It only happens when I pick it up after hours being charged. (Mine is in the wall charger, not usb to a PC). Once it starts working, its fine while plugged in.