My best guess is the window motor or regulator has crapped out on you. Sorry bout your luck man
This happened to me on my driver side window. I'd noticed my window had been moving kinda slow/odd and sure enough, one day i was rolling the thing up and about 1-inch away from being shut, it stops, never to work again.
Think the grand total to get it replaced was $500 cuz I simply could NOT figure out how the damn doors on our cars (s13, 91 fastback se, like yours) work.
soooooooooooooo.... unless someone else here knows how to dismantle the door entirely (just snap the door-panel off and im sure you will see what i mean) I'm-a-thinking your going to be stuck with an unfairly expensive repair
sorry