Invisible popup window

[Jeffrey Barish]

I created a popup window control for displaying a message.  It works fine in
my program on XP.  It works fine in a simple test program on WM.  However,
when I run my program on WM, the popup window does not appear.  The
dimensions are right.  The position is right.  It captures the mouse as it
should.  The only problem is that I can't see it.  I thought that it might
be hidden behind the main frame, but Raise had no effect.  I can't think
what else might be causing the problem.  Any suggestions?
-- 
Jeffrey Barish