I am begining to think that the mini-DVI port is fubar
Given you get something out of the display with your iBook it's doubtful it's the display. Granted it could still be the DVI port on your display that's at fault but I doubt that. So where do you go from here. A couple of options…
1) Find someone with a DVI PowerBook and plug it in to confirm the display's DVI port is working.
2) Plug you MacBook into any other DVI display to try to find out if the problem is there.
3) Go to an Apple Store and stamp your foot and spit out your dummy. Surely they have displays you can plug into to help you resolve your issues.