I have a 17" G4 powerbook and it has started to blackout. If Itunes is running, the sound contimues to play but I cannot see the screen or turn it on. I have set the energy savers to never but still the same. I have reset the computer by unpluging the unit and taking out the battery andholding down the power button for 30 seconds and leaving it off for 30 minutes. The proble continues. I can sometimes see something in the background but I must for a restart to get the screen up and running again. Can anyone help solve this problem