My window switch went bad, but it was obvious since the driver's switch broke off in my hand. The switches do go bad frequently enough though, that I would start there. Also, I'm sure it's cheaper and easier to mess with than the regulator.
The other thing would be to make sure power is actually getting to the door. As in, broken wires somewhere.
2009 PBM GT
Under the Knife Again
Wiseco Pistons, K1 Rods, Johnson Lifters, BLP Keep Hatin' PDS Cam, Roto-Fab, BLP Ported Intake and Throttle Body, Kooks 1-7/8 long tubes, XForce Varex Catback, ZL1 Converter, Camaro Trans Pan/Filter, GXP Brembos
Breyton GTS-AV Wheels, 6k HIDs, Holden Steering Wheel and Paddle Shifters, Eibach Springs, 35% Tint
Tuned by Day Tuning