Hey,
I have an older iBook (its an older "new" model, ie it has the newer font, not the old iBook font). When I try turning it on it just gives me a gray screen nothing else. I've tried the repair discs and reinstalling the software, but it just spits out the disc right away or does nothing at all. Just the gray screen. I am unable to see what model or RAM, etc. Any ideas?
Restart while holding command + s down till you see a black screen. Type fsck -f and wait for process to finish. Type reboot when process is finished. Hopefully your computer will reboot.
Also, did you try your hardware test cd? That might give you some clues...