rc2, xorg, and matrox g550 troubles

Hi,
I install 5.3-rc2 and tried to install xorg. 
I've a 64mb agp matrox g550 graphic adapter.

I'm loading the mga module through loader.conf. Here are my loaded modules:
%kldstat
Id Refs Address    Size     Name
 1   11 0xc0400000 5cdad0   kernel
 2    1 0xc09ce000 57dc     vesa.ko
 3    1 0xc09d4000 16620    mga.ko
 4   14 0xc09eb000 537f0    acpi.ko
 5    1 0xc2885000 17000    linux.ko

X does not work when I launch with startx, I get a "no signal" error from my lcd screen. I have manually kill the server with "ctrl alt backspace". After killing the server, the following error appears:
------
(==) Log file: "/var/log/Xorg.0.log", Time: Fri Nov  5 00:26:58 2004
(==) Using config file: "/etc/X11/xorg.conf"
(EE) MGA: Failed to load module "mga_hal" (module does not exist, 0)
xterm:  fatal IO error 32 (Broken pipe) or KillClient on X server ":0.0"
login:  fatal IO error 32 (Broken pipe) or KillClient on X server ":0.0"
X connection to :0.0 broken (explicit kill or server shutdown).
------


If I don't kill the server after a few seconds, I can't kill it anymore. I can't swith back to a console, as all my screens stay black.

I checked the x11 driver direcotry and indeed there is no mga_hal.o in /usr/X11/lib/modules/drivers/

I googled a bit around and found that I may be I need to copy the original matrox linux drivers (mga_hal.o) to the directory (mentionned above). But it still doesn't work, now I get the following error:

-----
(EE) MGA(0): MGAValidateMode from HALlib found the mode to be invalid.
        Error: 0xb1901112
(EE) Screen(s) found, but none have a usable configuration.

Fatal server error:
no screens found
-----

Is someone running the g550? perhaps also in dual mode? If so, could you please send me your xorg.conf file?

If you need more info, please tell me.

Thx a lot
Didier