I have fixed my window that would not stay fixed.  As you may recall,
in the last chapter of this particular frustration, Matthew told us that
the problem was that the nylon nut had broken.   I found this to be
basically true.  The problem was to get another one.  I made mine in
the following way:
I went to the hardware store and found a hexagonal nylon nut that was
very close in dimensions to the nylon nut in my window.  (I think it
cost $.75).  I drilled out the hole a bit to fit on the window mover
stub (no idea what a better name for this thing would be).  I then sanded
the nut to be only slightly larger thickness than the original nut.
Finally I milled out a notch on the top and on the bottom which is necessary
for holding the track to which the window is attached.  I don't think
it is necessary to use a milling machine to cut the notch, probably a
sharp knife can also be used.
The upshot of this is that my window now seems to work once again without
buying a new window cranking apparatus.
Stuart