At ajax's request, here is a paste of the gdb output when the server was
compiled with: -march=opteron -O2 -pipe -g:

noisy root # gdb `which X`
GNU gdb 6.0
Copyright 2003 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "x86_64-pc-linux-gnu"...Using host libthread_db
library "/lib/tls/libthread_db.so.1".

(gdb) run
Starting program: /usr/X11R6/bin/X
Deleting unknown breakpoint type 25

X Window System Version 6.8.0
Release Date: 8 September 2004
X Protocol Version 11, Revision 0, Release 6.8
Build Operating System: Linux 2.6.11-rc4-mm1 x86_64 [ELF]
Current Operating System: Linux noisy 2.6.11-rc4-mm1 #6 SMP Tue Mar 1 08:02:34
EST 2005 x86_64
Build Date: 02 March 2005
        Before reporting problems, check http://wiki.X.Org
        to make sure that you have the latest version.
Module Loader present
Markers: (--) probed, (**) from config file, (==) default setting,
        (++) from command line, (!!) notice, (II) informational,
        (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: "/var/log/Xorg.0.log", Time: Thu Mar  3 08:42:51 2005
(==) Using config file: "/etc/X11/xorg.conf"
Using vt 8
(WW) NVIDIA: More than one matching Device section found: Card0
Unable to query/initialize MicroTouch hardware.
(EE) PreInit failed for input device "Touchscreen1"
*** glibc detected *** double free or corruption (!prev): 0x0000000000b88700 ***
Program received signal SIGABRT, Aborted.
0x00002aaaab29bc49 in raise () from /lib/tls/libc.so.6
(gdb) bt
#0  0x00002aaaab29bc49 in raise () from /lib/tls/libc.so.6
#1  0x00002aaaab29d14e in abort () from /lib/tls/libc.so.6
#2  0x00002aaaab2d4b84 in malloc_usable_size () from /lib/tls/libc.so.6
#3  0x00002aaaab2d5646 in free () from /lib/tls/libc.so.6
#4  0x0000000000447c8c in xf86DeleteInput (pInp=0xb88860, flags=19087)
    at xf86Helper.c:350
#5  0x000000000042fb3a in InitInput (argc=19087, argv=0x4a8f)
    at xf86Init.c:1051
#6  0x00000000004911e1 in main (argc=1, argv=0x7fffff9bf428, envp=0x96b000)
    at main.c:391
(gdb)


The machine itself is a dual opteron.  Whatever details y'all need, I'm happy to
provide.