I doubt the caps have anything to do with whats going on here. It appears this is using the ever so popular tripath class-D audio stage.

They pull some serious current at high volume. Check for any in line fuses for opens on the USB port itself, and where it comes in at on that box. Check the usb cable for breaks. Thats a high current so anything is possible.

If everything check out there, then your USB audio controller on the PCB has died.