I can confirm this odd behavior on my EeePC (even on AC power) using 9.04 UNR. If I modify my current brightness using the hotkeys, the screen will later change its brightness to something else. Also, I don't think it is related to going into or out of idle, and I can't seem to notice a particular trigger for it.
The only work-around I have figured out is to change the brightness level from within gnome-power-manager and not touch the hotkeys.
I can confirm this odd behavior on my EeePC (even on AC power) using 9.04 UNR. If I modify my current brightness using the hotkeys, the screen will later change its brightness to something else. Also, I don't think it is related to going into or out of idle, and I can't seem to notice a particular trigger for it.
The only work-around I have figured out is to change the brightness level from within gnome-power-manager and not touch the hotkeys.