That sucks big time. A friend who owned an engine shop had his daughter's Trans Am in the shop, it seized at a traffic light. They had the engine ready to pull, and he was carrying the alternator over to the parts pile when he noticed the pulley wouldn't turn! He hollered "Whoa!" and tried turning the crankshaft. It was free! The serpentine belt stopped the engine cold. At least they hadn't got the engine out yet.
I'd try a pump by another supplier. Was yours made overseas, by any chance? China, Taiwan, the Phillipines, Korea, all crap. A rebuilt American pump is far better than a new one from those clowns.Or even a good used one!