I just noticed that latest xorg-server-1.12.1-1 is crashing
when using octave with fltk interface.
Reverting to xorg-server-1.12.0-5 solves the issue

$ uname -a
CYGWIN_NT-6.1-WOW64 MARCOATZERI 1.7.16s(0.261/5/3) 20120517 02:19:46 
i686 Cygwin

attached Xwin log.

To replicate run octave and at prompt just digit:

   graphics_toolkit("fltk")
   x=1:10
   plot(x,x)

Regards
Marco