Comment 17 for bug 137225

displayconfig-gtk sets up xorg.conf to use Xinerama (and "zaphod" mode). The new intel and ati drivers don't support Xinerama any longer, and xrandr must be used, like described in that Intel howto linked above. Therefore displayconfig-gtk must be fixed. OTOH, the X server should not crash because of this configuration, but just ignore it and give a warning message, in the ideal case.