Autozone sells a 3M Glazing urethane, not to be confused with silicon or other sealers.
Using it without the specific glass primer it will hold just fine,and as Alvin mentions it dries to almost solid rubber.
Make sure the glass and channel are as clean as possible before bonding.
(Tip: Wear rubber/latex gloves)
Give it 24hrs or so to cure before operating the windows.
I used a non original seal on my 50s frames but used urethane to secure the lower sash to the door glass. Worked like a charm!
Last edited by jockbolter50; 05/16/2010 7:17 AM.