allright, weird problem. i use debian sid, 2.6.23 and xorg 7.3 and gnome 2.20. i got a Asus G1 laptop, and i got asus-laptop module loaded... all acpi buttons/leds work fine... except brightness:

on GRUB - works
on VT (console) - works
on GDM - works
login... (xorg) - pressing the brightdown button makes the screen the darkest it can be, pressing brightup changes bitween dark gray and very dark gray. if i unload "asus-laptop" module - it works! (but then nothing else works)

so my idea is xorg is trying to use it's own brightness tools and they conflict with the asus-laptop module...

when i was using feisty & 2.6.22-2 & xorg 7.2 & a custom dsdt table it worked...

anyone has any idea??

I choose K menu - system - nvidia settings (I use KDE - Nvidia G 8400 M graphics card)

Then I can change various settings, inclusive brightness - remember to save changes, to make them permanent.

:-)