I came across this fix, sadly i dont remember from where. It so that you can use the Fn+Up/Fn+Dn to adjust desired brightness on your display. This worked on a lenovo U350 running 10.04

open terminal type in:

sudo nano /etc/default/grub

Change:
GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash”
to


GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset acpi backlight=video"

also change:

GRUB_CMDLINE_LINUX_DEFAULT=”"

to

GRUB_CMDLINE_LINUX="nomodeset acpi backlight=video"

then run:

sudo update-grub