Walls and Ceilings - re:water damage wall help

I've submitted 2 questions w/no response and the interim things have changed. The leak is NOT from the foundation because only around the sill is there a problem which seaps into the interior wall and marble interior sill. Well, my question is if there is a water drainage problem accumulating inside the window where would it be coming from. I have a new roof and the gabels show some moisture. There is no ventilation/a/c duct work in this area. Any suggestions or possibilities around out there?

finding a water leak can be really maddening. the
source can be many feet away from your window. i
found one once that started under the shingles in
my valley, then followed a rafter until it ran into some electrical conduit and followed that until it finally started dripping into our room
at least 20' from the source. stopped another leak
on a different project (after 4 other attempts
failed) by finding out that it was coming from an
inside corner where the siding met a full 25'
from the window it was leaking into. so all i can
tell you is the next time it rains get up in your
attic and start looking for a leak, paying particular attention to spots where valleys meet
and any venting in the roof.
good luck!