Johan: You may want to try setting HorizSync and VertRefresh on the liveCD /etc/X11/xorg.conf to the exact settings that your monitor manual specifies (and then restarting gdm) to see whether any new options become available...
Johan:
You may want to try setting HorizSync and VertRefresh on the liveCD /etc/X11/xorg.conf to the exact settings that your monitor manual specifies (and then restarting gdm) to see whether any new options become available...