I used to be able to adjust the brightness with F5 & F6 but now for some reason it doesn't function? When pressing F5 or F6 a semi transparent brightness control box appears and nothing happens with the actual brightness even though the marker increases and decreases.
I can adjust the brightness from system preferences/displays.
And I don't have the function keys ticked in the option.
Any help with this much appreciated. This is so frustrating, why suddenly it doesn't function?
Oh, and it's a 15" Unibody MacBook Pro.