How to fix a rear door window that won't go up.

I own a 4 door 2005 Pontiac Grand Prix base model that I love. While moving some stuff out of the back seat I accidentally bumped the door switch on the rear driver's side door and it came down about 3 inches before I could stop it. Immediately I tried to roll it back up because it is snowy and cold here and nothing happened, no sound, nothing. I next tried to close it with the driver's door switch but again nothing, not a sound. Took enough off the door to get at the regulator and applied 12 volts of power to the motor and the window closed quickly and quietly. Left the regulator unplugged so that the window can't open until I find the cause of the problem. The fact that the window closed quickly and quietly seems to suggest that the regulator is good. Not being able to close the window with either the driver's door and rear door switch is confusing. Help!