Yeah, that was just a wisecrack about the new belts.

What you need to do (like I said) is verify that the pulleys all line up properly with each other. None are loose & wobbly. I know you said they all spin freely, but they also have to be straight & true. Any pulley that you can "tilt" at any angle can cause the belt to derail & shred itself.

Now about a seized pulley... If the alternator or PS pump were seized, you'd feel that when you try to spin them. Not so for the AC compressor because it's pulley will freewheel when you're in there checking it.

Next, check the AC pulley. Look like any burn marks? What I'm concerned is the AC compressor being seized up, but you can't tell that by spinning the pulley. That pulley has an electromagnetic clutch that engages when you turn on the AC. That's a little harder to check.

Have someone start the car while you watch the pulleys (with the new belts installed). Have them switch on the AC while you watch. If you see any distress at that pulley, have them immediately switch OFF the AC. The you'll need to fix the AC, or disable it so it can't turn on.