I am in the middle of fixing my window. It was getting stuck and pulling forward, then almost impossible to go up by itself. I replaced the regulator $140, (on advice from the shop I bring it to) but then realized it was probably the rubber track that was the problem. I got a new rubber track ($120) and it seems to work fine. Now I just have to figure out a way to reattach the plastic brackets to the glass.
I said all that to say this, I would recommend opening up the door panel and checking it out, you can probably figure out what is the problem. Either the motor, regulator or rubber track.