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
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset acpi backlight=video"
GRUB_CMDLINE_LINUX="nomodeset acpi backlight=video"