Comment 35 for bug 61184

While I was experiencing the same symptoms, Feisty has this bug fixed. The .fdi patches in this thread are already incorporated into Feisty.

What I am experiencing is outlined here: http://www.thinkwiki.org/wiki/Installing_Kubuntu_6.10_on_a_ThinkPad_X60s_2 and also here: https://bugs.launchpad.net/ubuntu/+source/linux-source-2.6.20/+bug/87028

Current workaround is to blacklist video.ko module (echo blacklist video >> /etc/modules.d/blacklist). Brightness controls now work, but gnome-power-manager OSD does not know the brightness (it thinks it's always full).

Interestingly enough, using 'echo "level 4" >> /proc/acpi/ibm/brightness' does work and gnome-power-manager's OSD does report the right brightness. Something should be probably done here.