Have you tried taking out all drives except for the optical, and then giving it a go? That way it would force it to boot off the disc, or not at all.

Sometimes my b&w G3 would like to sit around and scratch its head for about 5 minutes before deciding to boot from a CD, so I would go to the Open Firmware (Command-Option-O-F) and type

, then return. That will put a Mac OS logo on the screen, then sometimes the Mac will go into action straight away. Works with hard drives as well.