The only way my window does not squeek when its closed all the way is if I open it slightly.
I tried Shin Etsu grease, and it did not help.
I tried jamming strips of foam inside the molding which helped for a while but the squeek is back.

Anyone know what is causing this ... and what I need to do to stop this permanently ?

 

Shin Etsu should do the trick. My tint is all the way to the edge of my window and I use the grease to lubricate the rubber to prevent binding where it meets the tint. I need to re-apply again soon. It has been a while. If the squeak is from where rubber meets glass then the grease should work. Are you sure you applied it to the right area?

 

As above, you have to make sure you're greasing everything, including the hard rubber inside the window frame at the top edge of the glass. The squeaking you're hearing is the top edge of the glass rubbing the rubber seal where it's seated. Make sure you also get ALL the rubber around the door frame too with a generous coat of grease.

 

Aerospace 303 worked like a charm for me.

You spray it on a rag, and then gently rub it all around the window sills from outside facing the car. And then wrap the rag around your finger and ( while the window is down ) stick your finger till you feel the glass edge of the window and just wipe away.

It's almost magical how good and quick it worked. Applied it about a week ago, and still going perfect.

 

I got 75% reduction in squeak by using only Silicone spray on a rag and working into the vertical and horizontal channels. Probably would have achieved better results if removed Window regulator, then manually lower window as far down as goes, thus allowing easy access to ALL of the vertical channel. What amazes me is how tight the window fits judging just by manipulating the window by hand ( disconnected from REGULATOR), even after the Silicone job. These window motors and regulators must be very rugged.