Comment 6 for bug 1232952

I found a workaround here: http://ubuntuforums.org/showthread.php?t=2181534

create the file /usr/share/X11/xorg.conf.d/20-intel.conf with the following content:
Code:
Section "Device"
        Identifier "card0"
        Driver "intel"
        Option "Backlight" "intel_backlight"
        BusID "PCI:0:2:0"

EndSection
...and log out and back in again