window screeching noise - what could it be?

here's the current problem. BTW, car has 120,xxx miles, so she's getting up there

my driver window, when i roll it down, starts making a whining screeching noise that is pretty loud, starting at about 1/2 open position and all the way down. no noise on the way up. it works nice and quick, so I do not think it's a window motor. my mechanic (not the dealer) thinks it could be something rubbing inside and will take the window apart on the weekend. The noise is towards the back, and I can see 2 marks in a form of a line on the window. Any help would be greatly appreciated. I should mention that i had tint on both front windows taken off about a week prior to this noise appearing (to pass inspection in NJ, tint is illegal on side windows). I called the tint guy, he said no way the tint/no tint would cause this.
I cannot believe the car has 120,xxx and how nice it's running, still extremely strong, solid and sound.


