I've overlooked this one a lot. I have a 10.5.6 disc so I don't have to do the combo update. I do know that it does happen before I install the other updates sometimes. (I do a lot of tinkering so I've installed the OS about twenty times.) As of right now I have the updates installed. I don't have any other major issues, so I just haven't care too much to look into it. I think I've repaired the permissions on the disk, but I'll check again today. That's a common issue with the DellEFI. I've also noticed that when it happens any attached USB devices will be turned off, i.e. my thumbdrives have LEDs to indicated power and activity and they are shut down when it hangs at boot. But I don't always have them plugged in when it happens.