IIRC, three KC-135s have blown up from fuel-tank ignition. (Four if you include the most recent tragedy in Kyrgyzstan). Two were on the ground undergoing maintenance; one was on descent for landing (it had off-loaded most of its fuel, so the tanks were all nearly empty).

The KC-135 explosions all happened long before TWA 800. At the time of the last tanker explosion (the in-flight one), I was flying over Iraq on nearly a daily basis. (About 1993). The end result was the tankers were required to land with a hideous amount of fuel (I think it was 20,000 lbs), and it severely restricted their off-load ability. It meant only one refueling per mission instead of two, and shorter sorties for me.

After TWA 800, I worked for EIA. We had to land with a significant amount of fuel in the center tank (I think it was 10-12000 lbs) unless it was an emergency, or if it had scavenge pumps. The belief was all the incidents had been caused by overheated fuel pumps; left running with no cooling fuel.

I'm with Rick. Unless a terrorist got an incredibly lucky shot (from a boat) with a MANPAD, the "errant Navy missile" theory is best suited for the script of a Lifetime or Bravo-channel movie of the week.