That's too bad Ed. I'm curious what you mean by the "complete autofocus module." I assume that you've checked all the switches and menu items that could affect focus (I've bumped the little switch by the lens mount before when changing lenses and it took me forever to think about that)?
Good luck with whatever the problem is, and welcome to Nikonians.
Ed, Just curious, but how did your focus failure start to show up?
I just got back from a cruise, 1st time to really put my new D800 through a test, I noticed that on a couple of occasions, I could not get it to focus right off. I had to move the focal point around in the image to get it to focus. I was shooting in Matrix using AF-S and a 28-300MM lens. Perhaps mine difficulty could have been just not enough contrast in the image I was shooting for it to lock on.