I have a G4 Dual 1Ghz Quicksilver. As of recently it won't stay powered down when I say "Shut Down" in the software menu. Restart works fine, everything else is normal. I can power it down by holding the power button for a few seconds, but cannot start back up simply by pressing the power button again. I have to remove power from the computer (unplug it) and reapply it a few seconds later. Once I plug it in it begins to reboot on its own before I've even pressed the power button. I tried resetting the PRAM. Seems like a hardware issue, bad switch somewhere perhaps. Any ideas?