I just went and bought a new screen for my PowerBook G4 today!
Now all I have to do is wait 3-4 days. Finally, I'll be able to use it as a laptop, except I don't have a battery…
What sort of adaptor are you using? If you have an adaptor with DIP switches or a dial, you might want to adjust it to force the monitor to run at either 640x480 or 800x600.