I just installed the latest security update on my PB G4 1.5 17". I also installed the Quicktime upgrade. After the required restart it comes up to the white screen and the progress circle just keeps on spinning. I shutdown and restarted twice with no luck. The machine is purely vanilla and has never once had an issue. In fact, I have never had any Mac issue. I am not sure where to start troubleshooting this if I cannot get it to boot. Looking for suggestions.