I would reboot into Recovery Mode as root and try a :
and afterward do a fresh reboot into normal boot to test the changes(if any)...
If that does not work reboot again into Recovery Mode and this time type:
This will update your xorg.conf.
To test the new xserver type:
If successful consider moving the new xorg.conf to /etc/X11 for the changes to become permanent:
X -config /root/xorg.conf.new
and tehn reboot into normal mode.
cp /root/xorg.conf.new /etc/X11/xorg.conf