Comment 11 for bug 74284

It's still reproducible. That is, I can't adjust brightness using hotkeys after acpi video module is loaded (assuming gnome-power-manager is not currently loaded).
Blacklisting the video module is still a valid workaround.
It has also been reported as bug #140782, but it has been incorrectly assigned to kde. Comment <https://bugs.launchpad.net/ubuntu/+source/kdebase/+bug/140782/comments/20> has another valid workaround.