While it's the anchor mentioned in the post above me about 75% of the time...
My driver's window went out last night....
After pulling it out, I discovered the tube that the spring/cable runs in had broken off right at the motor.
I thought about taking it to work and boring out the body and replacing the tube with new poly tube and epoxying it in.
Problem is, it's metric tubing 10mm OD x 6mm ID...
I could only find 1 source for the tube and it was a minimum order of 25 feet at $.53 a foot. And even then I wouldn't be 100% sure it would work.
The other option is Ebay. Right now there is a used one for $70.00.
Long story short, I bought a new one from Partstrain.com, $110.50 shipped....
I will most likely purchase the tubing and try my fix. If it works I'll have a spare. But right now I've got to fix the XJ as it's my daily driver..