I’ve discovered that /var/log/kdm.log is reporting some errors:
(EE) Failed to load module "type1" (module does not exist, 0)
(EE) Failed to load module "freetype" (module does not exist, 0)
(EE) AIGLX error: dlopen of /usr/lib/dri/mga_dri.so failed (/usr/lib/dri/mga_dri.so: cannot open shared object file: No such file or directory)
(EE) AIGLX: reverting to software rendering
Driver not XRANDR 1.2 capable, ignoring DISPLAYMANAGER_RANDR_MODE_* settings
Can you help to fix them ?
What video driver are you using?
My gfx board is a Matrox G400DH.
Kernel driver: matrox_w1
Driver: matrox_w1
Peripheral: MGP G400 AGP
I suspect that the error is exactly what it says. Your driver does not support the requirements of XRANDR thus XRANDR can not be used.
From what I found on the web, it seems the Mesa development team is no more supporting the mga_dri.so driver. No more 3d hardware acceleration for Matrox boards. 
Regarding the “type1” and “freetype” errors: I had these because the related packages were not re-installed after recovering from a big crash.
To remove the error entries, I edited xorg.conf and removed the lines
Load "type1"
Load "freetype"
from the “Module” section.
As for the missing mga_dri.so error, it did not really matter as redering then fall back to software rendering.
A trick to remove the error is to remove
Load "dri"
and/or add
Disable "dri"
in the “Module” section.
Anyway, mga_dri.so is now back in Mesa for openSUSE 11.3 (you have to install the latest Mesa package from the Factory repository). 