X11R7.5 doesn't like the (default) locale C.UTF-8.  If I start the 
server with 'LANG=C.UTF-8 /usr/bin/startxwin.bat', the server exits 
immediately, and the log has complaints about the locale.  If I instead 
use 'LANG=en_US.UTF-8', there's no problem.  I've attached both logs and 
cygcheck output.

Ken