Hi - we have a powerbook that is not completing the boot sequence.
After pressing power button, we hear the boot sound but the screen remains black. After the sound is done, the machine seems not reacting to any request. Even shutdown (that is press the power button again) is not producing any effect.
This happens no matter which key combination we tried. Namely we tried PRAM reset, safe boot, video card reset.

thank you in advance!!!
v.

Have you tried to boot with the system or install disk ?

... now it started to work again ... it seems it just needed to stay quiet for a few day (it doesn't make sense) ...

I had an iBook that acted like that. It turned out that the motherboard went, and needed to be replaced. Very expensive.

I've got the same problem with a PowerBook 15-inch FW-800 with Tiger 10.4.3. I'm able to boot only by pressing Command-S or Command-V keys (single-user or verbose modes).
This problem came after a boot from Apple Restore Disc to run the Disk utility.