Probably your switch. I had the same issues and that was my problem.
A good maintence tip..... About every 6 months or so when your car is dirty. Crack your windows down, with a can of WD40, shove the tip in the tracks (so WD40 doesn't get on the glass or in the car) and spray them down. Roll up the window a couple times and spray again. It will clean out the tracks and help lubricate them a little bit. You could use silcone spray but i find it too messy honestly. Doing this on a car thats never been done to before it will drastically improve window roll down and up times. The WD40 will of course leak out the drain holes on the door and down the rocker moldings. This is why I recommend doing it when the car is dirty. You should try it some time, probably the reason i've had very little if any power window problems on my cars.
BTW, it does work. I had my drivers door panel off awhile back, my tracks were as clean as a wistle and yes the silicone was still there so the WD40 didn't wash it away. I went ahead and reapplied some silicone since the best time to do it is with the door panel off the car.
