>     (modify-frame-parameters
 >      (selected-frame) (list (cons 'font new-font)
 >                 (cons 'scroll-bar-width 6)))))

What happes is that when we ask Windows to change the frame's size, we
don't record the new sizes.  When we ask Windows to change the scrollbar
width, we start again with the old sizes.  I can handle this case by
commenting in some code in w32term.c as in the attached diff.  But that
code was commented our for a reason.  So I don't know what to do.

martin

PS: I don't know why it worked earlier.  In principle, the potential for
this bug was always here.