My pioneer vsx 930 k has an issue when playing music via USB. It plays great for a couple of months and then out of the blue it just stops reading and playing. I've tried other USB drives with music on them and it still won't play. I also turned the unit off for a period and still it won't play. The only way I can get the USB playback working again is to reset the amp which is a pain as I have to set it all up again. Anyone know how to fix this?