I am not sure if it is relevant or not but I am having this exact
same
problem with F11 on my Dell inspiron 2650 laptop. The last time it worked,
was during F11 devel. I have to boot it with pci=noacpi to get it to
work at all.
I think this is a known gnome-power-manager problem. Fiddling with the
brightness keys fixes the problem for me on my MacBook.
Cheers,
Debarshi
--
One reason that life is complex is that it has a real part and an
imaginary part.
-- Andrew Koenig