Today driving home from work I pushed the window down button for the drivers RH side window it went down a few inches and there was a loud bang and the window stopped. Pushing the button causes no movement of the window but you can still hear the motor running. The window is completely free from any mechanical mechanism as I can push the window both fully up and down by using my hands on the glass. I obviously haven't had a chance to take off the door cover and have a look but can anyone diagnose the problem, required parts and expense from this?