the electric lift on my car on rear right side window has stoped opening/closing the window. I can hear the "motor" run if i try to open it, but window wont open and after some driving the window itself sink's and theres a small gap at the top of the window, i can rise the window with my hands to close it...

Anybody know what might be the problem ? havent opend the door panel yet, but guess i gone have to do that to fix it ofcourse but would be nice to have a slight idea about what the problem might be before i start banging my head in there..