The problem isn't the motor - the bracket that holds the window in the door loosens and doesn't push the window up evenly (too far toward the front), so it binds up in the tracks a bit. This is a VERY common problem on the VX - you will find many threads posted about it. Anita's suggestion will help a bunch, though. There are other more permanent fixes posted, too.
I am actually having mine replaced right now under my extended warranty. Yay!
Good luck!