Screen brightness setting always reverted to dim on boot-up.

Followed instructions in blue at:
http://forums.linuxmint.com/viewtopic.php?f=42&t=45271&p=378949&hilit=xbacklight#p378949

installed xbacklight.
added acpi_backlight=vendor to grub file.
created custom keybinding for xbacklight +50 and xbackglight -50