I was hoping someone else had had this experience before, all I can tell you is that one of my back windows has a simuliar problem. I don't notice jumping though. My problem is that the window motor is not strong enough to bring the window up anymore.. it needs replacing. The ford dealer wants $175 to do it (I think thats what they quoted, been a couple summers ago). The back windows get worn down from sliding up and down on the top's weatherstripping.
------------------
Rick
My 89lx(updated 2/21/2001)
My 97 Cobra