Turn the key and everything shuts down

Electrical problem
V8 Four Wheel Drive Automatic 130000 miles

I went to start my truck, I used the key fob to unlock the doors and when I opened the door all the lights came on. When I put the key in the ignition and turned it over it didn't fire right away. When I went to turn the engine over again everything died. Everything went dark and none of the electrical system worked. I waited about 20 minutes and tried it again, the power was back on at this time. I had done some research and found that it might have been the neutral safety switch. So this time when I went to start the truck I turned the ignition on and took the gears through all of the positions and and then back to park making sure that I was all the way into park. This time the truck started. I let it run for a minute or so and then turned it off. I went to then go start it again and the same thing happened, I got one click of the starter and then all power went out. I tested the battery and have the required 12 VDC coming from it. I have read that it may be either the security system or the neutral safety switch or the ignition system.