How to solved Brightness key Acer Aspire on Ubuntu 10.x or 11.x ?
In my sample using ubuntu oneiric ocelot 11.10.
sudo gedit /etc/default/grub
Change GRUB_CMDLINE_LINUX=”” to GRUB_CMDLINE_LINUX=”acpi_osi=Linux”;
sudo update-grub.
reboot your system and enjoy!! The brightness button should be working now!