Comment 60 for bug 776999

I have a w520 running Ubuntu 11.10 64-bit with the graphics option set to discrete in the BIOS. I was experiencing the same system freezes when I tried to use fn+home/fn+end lcd brightness controls.

Adding 'nox2apic' to the boot options and the nvidia-specific EnableBrightnessControl=1 option in xorg.conf solved the problem for me. The brightness adjusts correctly and the OSD indicator works properly. The wireless kill switch and AC plug/unplug are all working fine as well.

It looks like other, more drastic acpi kernel options work as well, but I'm happy with this relatively minor twiddle. Hopefully this is something that will be fixed in the upstream kernel.