For some reason, the sound output balance on my Powerbook G4 keeps shifting to the left seemingly randomly. i get the feeling i am pressing some unknown keyboard shortcut. not a big deal but irritating n'ertheless
It's a known issue with that rev of the powerbooks. Search around a bit and you'll find a program that automatically centers the sound balance every couple of seconds. I don't use it since occasionally I actually want off center balance but it might work for you.
EDIT: Wow... iMeowBot is fast. (he posted the program I mentioned by the way)