I had a strange problem that happened today. I pressed the power button to turn on the PX-560 and a loud noise started blaring out of the speakers. Volume was all the way down, and I had not touched any other buttons besides the power button. The only way I could stop it was to unplug the power cord. I plugged it back in and powered it up, and the loud noise started again. I tried it again the third and fourth time and it worked normally. I've had the keyboard for several years and this has never happened until this afternoon. Has anyone else experienced this and know the cause?