Not sure if this is related, but I had this problem with a wrist strap I use with my D700. From time to time my battery would show up as a dead battery even though it was recently full charged. I would take it out, blow on it a bit, put it back in and it would work fine. It got to the point where it was just a pain to keep doing this, so I took it in to the Nikon service center here. They said the pins on the battery can get dirty, and had a technician clean them off for me on the battery and also the pins inside the camera. Seems to work fine now and haven't had a falsely dead battery yet.