iPod Classic 160 frozen

I had the iPod Classic 160 GB connected through USB to my car and was playing the music through the system. Suddenly, the ipod froze. No sound. I disconnected it, but the screen stayed on the same graphic (Car Multimedia, Battery charging icon, Song Title, 'OK to disconnect'). It will not respond to any buttons on the front and will not turn off, as it usually does after a few minutes of non-use. When I plugged it into my PC to see if I could run a diagnostic and / or restore it, the PC says there was a malfunction with the USB device and it is not recognized. Any ideas?