Truck won't start! What could it be?

[Russ72C10]

Hey guys (and gals)... I need your help...

I went out this morning, started the truck right up. Went to the gas station... got gas. Went over to my parents place (to grab my 4-wheeler). Everything running great! I have to come back home real quick to get the keys for my ATV - but when I go back out to leave, the truck won't start. There have never been any signs or symptoms of a dying ignition component prior to this.

When I try to start it, it doesn't turn over. There's no noises at all. It simply does nothing. Lights, radio, etc all work fine. But I went ahead and swapped in a different (good) battery - same results. I also jumped the Neutral safety switch to be sure that was not the problem. Still.... no dice.

I had my dad come over to see what he thought. He did the ol' screwdriver across the starter trick... it sparked nicely, but even with the fireworks - still nothing happened. I may try this again myself to be sure though.

Anyone ever had such a totally random thing happen before? What could it be? I will replace the starter.... but if it's not necessary I'd rather keep that money in my wallet.