[Xorg] frequent crashes or how to debug?

[Melchior FRANZ]

I've installed X11R6.7 from CVS/HEAD and I'm not really happy with it.
While a self-compiled XFree86 4.4rc2 (and several older versions) works
flawlessly, X11R6.7 crashes routinely when I start some applications,
all of them linked against libqt.

But that's not why I'm posting here. The real problem is, that I am unable
to debug it. The logfile contains no hint (except a note that a signal 11
segfault occurred; my memory is OK). Running X in gdb freezes the machine.
I don't find a core file, although they are globally enabled
(ulimit -Sc 1000000).

Why don't I get a core file? What can I do to debug this problem?

I had to return to XFree86 4.4.rc2. :-(

m.



Linux 2.6.5, i386 (P4)
gcc 3.3.1 (SuSE Linux)
glibc 2.3.2
nVidia driver 3665 (apparently not the reason)