iPod Classic - Frozen on OK to Disconnect, will not turn off

My iPod Classic (120 GB model) has frozen on the "OK to Disconnect" screen. I ejected it from my iTunes, unplugged it from the USB, and set it aside. When I looked at it a few minutes later, it was still turned on, backlight and all, but stuck on the "OK to Disconnect" screen. I attempted to reset it by holding down the middle button, then the play button. I tried re-connecting it to iTunes, but it did not show up as connected. Is there anything I can do to get this to reset and turn off?

Thanks!