For the benefit of the Googlesphere, although probably of limited interest to anybody who reads this blog on purpose:
If your PowerBook boots with bizarro display preferences and won’t let you correct them, make sure you disconnect any dead external monitors, not just the live ones.
This came up when my 17″ external monitor went on the blink. I turned it off and rebooted only to find my PowerBook’s built-in display in the wrong configuration. I futzed around with it for quite a while before I thought to pull out the video cable for the powered-off monitor. Another reboot and the PowerBook was happy again.
Now thanks to a trip to Discount Electronics and $69 I’ve got a serviceable 19″ monitor in place of the dead one — not a bad outcome.