My video card is working fine, I have no screen problem.
I am trying to generate an xorg.conf so I did:

[ Logout ]
sudo service gdm stop
[ Move away xorg.conf.back and xorg.conf.fglrx-0 that were in /etc/X11 ]
sudo dpkg-reconfigure xserver-xorg
sudo X -configure

But this last command segfaults:

X.Org X Server 1.7.6
Release Date: 2010-03-17
X Protocol Version 11, Revision 0
Build Operating System: Linux 2.6.24-27-server i686 Ubuntu
Current Operating System: Linux nico 2.6.32-25-generic #44-Ubuntu SMP Fri Sep 17 20:26:08 UTC 2010 i686
Kernel command line: BOOT_IMAGE=/boot/vmlinuz-2.6.32-25-generic root=UUID=7447ab16-3406-442d-81e5-bb6a2d795205 ro quiet splash
Build Date: 21 July 2010  12:47:34PM
xorg-server 2:1.7.6-2ubuntu7.3 (For technical support please see http://www.ubuntu.com/support) 
Current version of pixman: 0.16.4
 Before reporting problems, check http://wiki.x.org
 to make sure that you have the latest version.
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: Fri Oct 15 16:06:11 2010
List of video drivers:
 i740
 ark
 geode
 siliconmotion
 mach64
 s3
 r128
 apm
 intel
 neomagic
 vesa
 trident
 chips
 s3virge
 fglrx
 sis
 savage
 rendition
 i128
 tseng
 ztv
 mga
 openchrome
 radeon
 ati
 nv
 v4l
 vmware
 cirrus
 tdfx
 nouveau
 sisusb
 voodoo
 fbdev
(EE) Can't load FireGL DRM library (libfglrxdrm.so).

Backtrace:
0: X (xorg_backtrace+0x3b) [0x80e938b]
1: X (0x8048000+0x61c8d) [0x80a9c8d]
2: (vdso) (__kernel_rt_sigreturn+0x0) [0x34d410]
3: X (xf86CallDriverProbe+0x182) [0x80b82d2]
4: X (DoConfigure+0x1c8) [0x816b898]
5: X (InitOutput+0x1da) [0x80b98aa]
6: X (0x8048000+0x1ebbb) [0x8066bbb]
7: /lib/tls/i686/cmov/libc.so.6 (__libc_start_main+0xe6) [0x467bd6]
8: X (0x8048000+0x1e961) [0x8066961]
Segmentation fault at address (nil)

Caught signal 11 (Segmentation fault). Server aborting

Please consult the The X.Org Foundation support 
  at http://wiki.x.org
 for help. 
Please also check the log file at "/var/log/Xorg.0.log" for additional information.

 ddxSigGiveUp: Closing log

Note the line Can't load FireGL DRM library (libfglrxdrm.so)

Note: I do have file /usr/lib/fglrx/xorg/modules/linux/libfglrxdrm.so

It is strange that it segfaults whereas I can use Gnome with no problem but well...
Might be related: I tried to install the driver from ATI's website recently, and from then glxgears crashes at start.

How can I generate xorg.conf in those conditions?
It might or might not involve solving the segfault problem.