If you are transferring a large batch of files (songs), and the USB connection is interrupted (this can happen with a bit if dirt on one of the contacts, etc), you might have a data corruption.
Press and hold the power button for 30 seconds, release, and see if the device will restart.
Since the Clip Zip handles the USB connection and all functions directly, it’s possible that the device simply froze. If it freezes, it won’t establish a connection. Kind of a Catch-22, isn’t it?
Try a reset, then plug in. You should be able to resume operation.
Bob 
