Sounds like a broken regulator(in one or more places) on the drivers front side...i heard the same noise your describing.

After a couple of day i had to push the window up or down(help it). Then it broke for good. I pulled the regulator and the electric window motor guts out and am waiting for a replacement regulator.Im assuming the motor it self is fine on mine, i'll check it in the morning.

Good luck(all my other windows seem fine, a four door '79 240D)

Im thinking thats what your problem may be.?