[xserver-xorg] - can't install, reinstall, remove, upgrade nor purge package

[Philippe Grenard <philippe.grenard@m4x.org>]

Hi all, 

I'm running unstable, and last time i did a dist-upgrade, the computer froze, 
and i couldn't do anything but hard-reboot.
Following that, the upgrade of xserver-xorg seems to be problematic. 
How to "make the system believe" that the package was never installed??

i've already done some dirty things like 
removing /var/lib/dpkg/info/xserver-xorg.* or editing /var/lib/dpkg/satus 
and /var/lib/dpkg/available to remove things related to xserver-xorg.

dpkg -i /var/cache/apt/archives/xserver-xorg_6.8.2.dfsg.1-9_i386.deb
gives : 

(Lecture de la base de données... 130627 fichiers et répertoires déjà 
installés.)
Dépaquetage de xserver-xorg (à partir 
de .../xserver-xorg_6.8.2.dfsg.1-9_i386.deb) ...
dpkg : erreur de traitement 
de /var/cache/apt/archives/xserver-xorg_6.8.2.dfsg.1-9_i386.deb (--install) :
 le sous-processus pre-installation script a retourné une erreur de sortie 
d'état 1
Des erreurs ont été rencontrées pendant l'exécution :
 /var/cache/apt/archives/xserver-xorg_6.8.2.dfsg.1-9_i386.deb

Any tips or help would be welcome : for the moment I just can't upgrade xorg!
 
thanks

Philippe