(Intrepid) Watch out for this bug..

Using Brightness Function Key Combination Breaks Keyboard and Menus
On some laptops using the function key combination to change the brightness can result in a loss of most keyboard control and an inability to fully open menus.

If you lose keyboard/menu control do the following:
Ctrl-Alt-F1 - Brings you to a text console
Ctrl-Alt-F7 - Brings you back to your desktop

https://bugs.launchpad.net/ubuntu/+source/gnome-power-manager/+bug/285323