What would cause a brand new V-belt to completly turn around so that the ribs are facing out in less than 25 miles of putting it on?

If there is nothing else wrong with the pulleys, idlers, etc, then maybe the belt wasn't in place on all of the pulleys perfectly, maybe jumped a groove or two. Did you change any of your idlers at the same time? I bought one that I refused to use because it wasn't perfectly flat like the original, but flared like a bell at the edge. It also was not as wide or centered like the original. I was hoping the flare would help keep the belt from going off the "short" side, but it made it worse. I even tried putting it in backwards, but the alignment was worse. I took the part back. That was a stamped metal pulley. Some people have knocked the "plastic" pulleys as being flimsy. I don't know what the pulleys they saw are like, but the black ones are a polycarbonate and last just fine. If they are the right size and shape, which this metal one wasn't, they should be fine, as I've used them, just the bearing wears out.

Another thought, though less likely, is the belt was defective.

Maybe one of your pulleys, more likely the idlers is not aligned. Maybe after you installed the new belt, one of the idler, tensioner bearings failed?

See if any of the pulleys has a damaged, chipped edge, shoulder.

The tensioner for both my belts are the alternator for the V-Belt and power steering pump for the Serpentine belt. I dont have the old belts because they snapped while driving down the highway. The waterpump pulley maves a little bit because the bearing is bad, thats getting replaces saturday. So the pulley moving around a little bit would be the cause of it, even though we left no free play in it?

Both belts broke at the same time? That's unusual. Makes me want to see if there remains a reason to cause that in light of your new belt problem.

I wouldn't think a little wobble in the water pump pulley would roll over the belt, but you may not realize how much wobble it has without the belt off. I can only suggest bad belt, something wrong with condition of the pulleys involved, belt was off a rib or two. Easy to do. For it to flip over, there had to have been some sort of unusual condition or not installed correctly. The likelyhood of it flipping on its own is extremely unlikely as the belt would have to be stretched with great force to get it to lengthen enought to flip. That'll be my 2 cents.

Did the water pump today, and have no pulley movement now. When I put the belt back on yesterday, the bolts that held the pulley to the pump were all loose. So I think that is what caused it. I also put the A/C bypass belt on since we had to take the A/C off to do the pump and just left it off. As far as both snapping, I think the V-Belt just came off, and since its behind the serpentine belt that it got caught up in that and caused it to snap taking both off. But seems all good right now, knock on wood.

Well that's good you have a plausible explaination for the belt rotating and the fix is as simple as retightening the loose pulley bolts. You probably wished you had noticed it when you put the belt on new 25 miles ago, but are glad it wasn't anything more than it was. Thanks for sharing what you think happened.