Bill

Had the same problem a while ago.  Here is what I did.

First   Replaced the little fiber washers on the pivot points there is three
washers per window.
Easy to do hex allen key removes the screws.  Unfortunately this only solved
part of the problem.  Now the water doesn't leak at the mounting ( pivot )
points.

I found the water runs down the outside of the glass and sits in the rubber
seal.  It then builds up and spills over into the inside of the vent window.
I read in the archives ( cannot remember the date ) how one member popped
open the vent window and filled the rubber groove with silicon, then closed
the window and let the silicon harden.  This filled the groove, bobs your
uncle, fixed.

I don't know if this works but I am willing to try

Ray.