Well it came as quitre a shock to me when I removed the USB stick after it had been left in for a number of weeks, I came to re-insert it and got a message on the screen i.e. "USB device not recognised" !!!, I tried the same USB stick in the rear USB Port and it worked fine i.e "USB Device detected", so clearly a problem had developed with the front USB port. I contacted Yamaha Tecdhnical Support by phone and they were very helpful, I tried to reset the USB Ports with thier help but to no avail, it was then that they suggested that the USB Jack or small motherboard which the USB Jack is soldered onto was faulty, so I ordered another complete unit as above and fitted it, and now it's all working fine. The moral of my experience is do not leave the USB device in all the time as it may cause the mother board to fail as in my case.