I have found a cure for this which has worked for me
- Ubuntu 13.04
- Packard Bell
- Intel® Core™ i3-2350M CPU @ 2.30GHz × 4
- Intel® Sandybridge Mobile
THE ORIGINAL PROBLEM
The F11 and F12 control the brightness, but although the tooltips showed that the brightness was changing, the screen didn't change.
I cured this by opening and editing the grub menu.
- Open Terminal with Ctrl + Alt + T
- I typed in
sudo gedit /etc/default/grub, entered my password
- I changed the line which read
- Saved and Closed gedit.
- in Terminal I updated the Grub with
- I re-booted the laptop
Everything is now working.