I am not sure if this is at all relevent to your situation but I have recently got a dead G4 Titanium powerbook to start again after being a paperweight for a while with the help of the people on here.
The problem on mine was the cmos battery was totally dead and it was this that was stopping the machine from starting. Unplugging it allowed the machine to start and after rebooting and shutting down a few times I reconnected the battery and it now works fine.
The thread for my query was still on the first page of this section under the title of Dead G4 Titanium powerbook.
http://www.mac-forums.com/forums/app...powerbook.html
Like I said, not sure this is relevent but it may just be the solution (hoping for you).
Trinimac.