I have had the same problem with my wifes Renault megane scenic. The window mechanism is made up of a wire running around the outside of a framework and the motor is like a winch. What happens is the wire comes free of the runner and stops the window working. It could also be electrical such as a relay or switch. You would need to take the door panel off to see if the wire has come loose of the runner. You should be able to go to a scrap dealer and find a replacement part easily enough.
Hope this helps.
Tony king, March 2010
