How ofter do you plug/unplug these USB devices? Is it possible that a jack/plug/wire got damaged? I've seen damage to USB interfaces cause very strange problems. It could even be the USB interface on a device has gone (perhaps a cap or some other component of the circuit has failed, which can happen with time).

If it isn't that, then it is a driver issue, and those are impossible to troubleshoot.

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs
-Chris