Help with electrical problems

I have a 92 Silverado Suburban 2500 4x4, 5.7l 225k+ miles.

I am at a complete lost to this problem and after searching the internet I have found no answer.

After driving all day, I come home and park my truck. One and a half hours later I go out to start it to go to the store and nothing. My interior lights, radio and AC fan come on, but when try to turn it over, there is a voltage drain as if the battery is dead, and nothing. No sound, no movement, everything shuts off. The windows, headlights, emergency lights, turning signals, all off as if there is not enought voltage. I took the battery to be tested and it is fine, fully charged. Then I broke out the multimeter. I have full voltage to everything: starter, soleniod, distro panel, fuseable link, fuse panel, computer. I have even beat the starter. The guy at the parts store said that it could be the nuetral indicator switch, which would explain no turn-over, but not explain why nothing else works.

Please help, I do not know what else it may be.

Could be bad battery cables, Check the positive lead at the starter voltage and have someone turn the key , and look for a drop there. Also could be a faulty ignition switch, the contacts get corroded/carboned up.

I tried that, but there was no chang e in voltage.

I have a buddy whose father is AST certified, and he came over to look at my truck. He said that it was the starter also, which would explain not turning over, but not explain why nothing else turned on. So he started playing with the battery cables. I have both side and top posts on my battery, so that when we tested connections, we used the top. The problem was with the side posts, which my truck uses. Apperantly the side post broke apart inside the battery just enough to provide the voltage, but not enough amps when cranked. Hence that is why only the cab lights came on and nothing else because they needed the extra amps.