I've had my D800 for about 15 months, and it will occasionally do the same thing. It may, repeat MAY, be related to pressing any button too soon after power-on. In any case, if I power the camera down and then turn it back on, the problem always goes away. I suspect that there might be some kind of digital timing sensitivity in the CPU or the buss. It's a minor irritation, not enough to warrant sending back to Nikon who might return it with worse problems.