I recently upgraded from Ubuntu 13.10 to 14.04. Everything is fine, except the brightness of my laptop screen. When I change the brightness the screen simply does not respond. I figured this was a graphics driver issue, but having updated and reinstalled all nvidia drivers the problem persists. It's rather nasty, as the screen is now permanently set to the darkest setting, making it almost impossible to see anything.

I also tried the solution proposed here: Ubuntu 14.04 - brightness problem in HP hybrid laptop
but this, sadly, didn't help either.

I have a HP Elitebook 8560w, with an nvidia Quadro 1000M and am running the latest nvidia-current drivers available in the apt-get repo's

For the record, I tried experimental nvidia drivers, which consequently crashed my entire OS. Therefore, I reinstalled 14.04 cleanly, yet this problem still persists