For those of you who experience failure of the master window switch, here is
how I repaired mine:
I purchased a working switch from a reputable ebay parts seller.  I bought
one that was lowest price ignoring the fact that the buttons were well worn
and the part looked VERY used.  I received the part, and then disassembled
the old switch. I replaced the pc board into my switch assembly since my
buttons still looked good, reinstalled the switch assembly into the cover
plate and all functions work properly.  I believe a new switch assembly
costs ~$100.  We'll see how long this one works!  For $25, I think it's
worth the labor I put into doing it myself.  AFA moisture being the culprit
as I've read from others, this is probably not the cause of failure.  It is
probably a bad diode or solid state component on the pc board. There is a
rubber cover that the buttons actually push into to activate a micro switch
on the pc board that I believe prevents moisture (from leaving the door open
during rain etc.) from getting into the pc board.  As with alot of
electronics failures that are notorious on the 3rd gen Max, it is just an
age/use problem.
Hope this helps someone out there.

Chris
90 & 94 GXE's