In your troubleshooting, did you happen to reset the PMU? It controls the sleep functions. Just a thought.
PowerBook G3 Series (M4753)
1. If the computer is on, turn it off.
2. Simultaneously press Shift-Fn (function)-Ctrl (control)-Power.
3. Wait 5 seconds.
4. Press the Power button to restart the PowerBook computer.
A hard reset might work if this doesn't. Remove the battery, then hold down the power button for 30 seconds. Wait five seconds. Replace the battery and push the power button.