Back Window Leak

I have a 2000 S-10 with a solid back glass, I notice the other day my back glass is leaking, I tore out all my panels and can't find it anywhere. Has anyone else had this problem and how did you fix it. The glass shop says it needs to be re-sealed but they wont guarantee my glass wont break. The water comes in at the B post on the drivers side and the truck has never been wrecked. Thanks for your help. Mark

Ive seen this before on chevrolets, take some water and pour it around the third light, alot of times that foam will not bond to the body of the car and get in the cab and as you turn the water runs along the inside frame work and will drip down on the inside, pour a good amount of water in it and shake the car back and forth to simulate turning to see if its leaking, if that produces no leaks then it might be the glass or possibly a body seam, a good glass man could take that glass out in 10 minutes without breaking, it is not a difficult job, ive been doing auto glass for 7 years, if they tell you it is hard to do go somewhere else because they dont know what there doing