For the last month my 15" AL Powerbook G4 starts repetitively beeping whenever the screen goes dim. It's definitely the system sound beep because it changes whenever I change the system beep (purr, ping, sosumi, etc.) The weird thing is the beeping, while continuous and rapid, is slightly arrhythmic. If I didn't know better, I'd say a mouse was tapping at the inside of the screen, trying to get out.
I'm totally stumped on this. Can anyone help?