After a clean install from live CD, fcn button f-6 and f-7 work to control screen brightness. After installing recommended updates from Update Manager, I lost control of screen brightness. I followed Ubuntu community recommendations to re-write X11/xorg.conf file. Having done this, the machine would not reboot/start. On restart the machine would hang at the Ubuntu splash screen. Accessing the emergency Terminal did not permit me to return to the original xorg file, because I was not the owner of the file. Eventually I re-installed 12.04.1 from live CD, but now I am afraid to install the updates. Would it be smart to uncheck all the X11 file update references from the Update manager and then update? I don't want to re-install again. EVERYTHING SEEMS TO WORK FINE WITHOUT THE UPDATES, but I now have over 200 updates pending! Any ideas?