My D300 is plagued by the body and lens not communicating. It happens sporadically. I have cleaned the contacts on lens and body, the camera works, but when I pick it up in the morning its malfunctioning. I'll be in the muddle of shooting and it goes down.
The aperture closes down, the autofocus stops working, the camera becomes useless.
I've seen a fair amount of chatter on the blogs about this, but no remedy except to clean the contacts -- which I've done thoroughly.