Can you try it on Ethernet to remove USB from the problem dimension? [i.e. physically remove the USB cable plugged between the player and PC - make sure the USB cable is not left plugged into the player or it won't boot properly].

[or if no Ethernet available, then use the Serial cable that came with your unit].

If you can make progress without the USB cable then that points the finger at the USB setup, but at least you can sync your files to the player.