So odd... adding
Code:
acpi_brightness=vendor
did not work for me. The keys were working and you could see the brightness indicator go up and down, but the actual screen brightness did not change.

I changed it to:
Code:
acpi_backlight=vendor
and that worked (found here: http://askubuntu.com/questions/12846...-an-acer-4741g). I don't know if this is a difference between Ubuntu versions or something else odd. I'm running 12.04, 64bit.