Sounds like just unseated chips, this was very common
for this unit, I have
4 myself. Take off the cover and push in all the chips checking for
corrosion. After you remove the top you can remove the motherboard on its
mounting plate from the bottom. If you pull out the titan cards you also
remove the video bios. Unless you have the old chip to replace the chip
the cards are attatched to, you can't boot the machine.
Apple recommended that when this started to occur, you picked the Apple ///
a couple of inches off the table and dropped it to reseat the chips.
I'm not suprised that they weren't the success Apple had wanted. :)
Adam.