iBook G4 Brightness/Volume Button Issue
After updating to Mac OS 10.4.3 I found that I was no longer able to use the hotkeys on my 12" iBook G4 to change the screen brightness or the speaker volume. In fact the brightness control wouldn't appear in the Display preferences either. Annoyingly it was set to a dull mid-range setting rather than the full-on setting I typically use when not in total darkness. Anyway, I'm not sure if it was the hard shutdown or zapping the parameter RAM (by holding down Command-Option-P-R after the bootup sound), but it's fixed now. So if you're having the same issue, I would suggest trying that.