After running with debug version of XWin compiled from the CVS per instructions in http://sources.redhat.com/ml/cygwin-xfree/2004-01/msg00160.html, I have so far been unable to reproduce the XWin crash.
I did notice that the icon in the task bar is different, I saw a focus w/OpenOffice + Evolution and Emacs stopped working, so I guess not everything that is currently committed to CVS is ready for release. Ãyvind