An iBook (Dual USB) computer with Mac OS X may stop responding after the display dims, or the computer is put to sleep.
Symptom
The computer stops responding if the display dims after a period of time, or in some cases if you put it to sleep. The only way to get the computer to respond is to restart it. You notice that this happens if the Classic environment is open when the screen dims or when the computer is put to sleep.
Solution
Download and install Mac OS X 10.0.4:
The update is also available from Apple Software Updates (http://www.apple.com/swupdates/).