Comment 3 for bug 140782

Confirming this behaviour on my Dell XPS M1710 running Kubuntu Gutsy - Fn+Up/Down work while booting (I assume they are still BIOS controlled at this point) until X and/or KDM starts. Possible duplicate/related to #140839 although symptoms are not quite identical (neither key works for me, while that bug reports that Fn+Down still works, though this may be due to differences with how KDE and Gnome handle this).
I can still alter the brightness through /proc/acpi/video/VID/LCD and dellLcdBrightness from libsmbios, and it was working fine before I upgraded earlier today.