Laptop panel brightness

[Ian Collier <Ian Collier comlab ox ac uk>]

I'm not running the whole of GNOME, but I am running gnome-power-manager
and gnome-panel among other things, so I guess this may be my fault for
having an unusual setup (and it may not be GNOME's fault at all, but I
suspect that g-p-m is doing it).

Anyway, my problem is this: I have g-p-m preferences set to default the
screen brightness to 15%, which is fine for most purposes.

On a bright day, if I press the laptop's screen brightness hotkey to
make the screen brighter, then some time between 5 seconds and 2 minutes
later, it automatically dims back down to 15% again.

What am I missing that would make g-p-m accept that I've changed the
brightness manually for the current session?

(This is under Fedora 14 with g-p-m 2.32.0, although it also happened
with earlier versions.  And for some odd reason, Fedora no longer ships
gnome-brightness-applet which would mitigate this problem.)

Thanks
imc