This winter, two of the power windows on my '07 A4 stopped going down. When I hit the window down button, either from the driver's door or the affected doors (front passenger and rear driver), there is a sound like the motor is briefly engaging, but the window doesn't move more than just a wiggle. The car is just out of warranty (of course!). I've read about power regulators and how defective they can be in this car--does anyone know what could be causing this problem? Thanks a lot for your input.