Sometimes after an update, it takes a long time for the Mac to reboot. However, if it stays on the same screen for more than 10 minutes, we can accept that there is something else going on.
As the machine starts from the DVD and can boot into Safe Mode, there is probably nothing wrong with the hardware.
Boot the machine in Safe Mode and remove everything from the Startup Items folder on your account.
Take a look in the Start Up items in the HD/Library and drag anything from there onto the desktop.
Restart the machine and see what happens then.
Let us know
My wife installed an update for MS office 2004 then restarted. The computer now hangs on the grey apple screen with the progress indicator spinning. I started up from the install disk and repaired the disk and disk permissions from the disk utility but this didn't help. The computer does start in safe mode but I don't know what else to try from there. She has a Macbook with intel 2ghz processor, 2gb ram and Mac OS X 10.4.10.
Any suggestions greatly appreciated. The genius bar is booked and she needs to work.