Christoph,
My co-worker was having the same problem at home. He was starting
XWin.exe by running it in a bash shell. This appears to not get all of
the paths set correctly and led to a crash when he tried to run KDE. I
had him run startxwin.bat to start XWin.exe and the crash stopped
happen
I experience segment faults from XWin, when I do a startkde on linux or
/usr/dt/bin/Xsession on aix with a XWin Display which has been started just before.
This fault will not occur when I do a xclock& first.
I use XWin with and w/o X11 forwarding with putty on windows and openssh on aix/linux.