I picked up a can of CRC Heavy Duty Silicone Spray from Walmart. It seemed to have done the trick. Thanks for the tip. I'll do a little further investigating when I take the panels off to change the speakers. To see if anything is loose or needs lubricating. The window still tends to vibrate when lowering.

http://www.amazon.com/CRC-05074-Silicone...3224&sr=8-1