My problem is that I can't change the brightness level of my laptop screen. I tryed to change it with the Fn key combination of my keyboard, and Ubuntu shows its brightness bar moving up and down, but the screen doesn't change the brightness.

I tryed with some scripts that I found at Google (that's one of that links http://ubuntuforums.org/showthread.php?t=1446943), but nothing works... Neither xbacklight nor backlight scripts.

Can someone help me with this problem?

(Sorry if there are some mistakes, my English is not very good...)