This weekend I started thinking, "What if the problem with the keyboard is a software problem. Maybe if I reload the OS it will work."

So I went to the repair shop and took my keyboard home. When I got home and turned it on, everything works properly! It looks like I have one of those intermittent problems on my hands.

I upgraded the firmware while I was at it.

I called Yamaha tech support. I want to ask them what might be causing this problem. Maybe a loose wire. Maybe a hairline crack on the circuit board. Remember, the problem was that the buttons weren't lighting up or working, but the LCD was on and the mic and keys worked.

Very mysterious.