I have a B&W G3 350 that is running 9.0.4 without any problems. I suspect that something got corrupted and suggest that you consider reinstalling (clean install) OS 9, reboot and then follow Apple's instructions and update to 9.0.4. After this, move your extensions and control panels, and fonts, etc. from your previous (old) system folder that you want to keep to the new one. Good luck.