I had the same problem last week on Tiger, except it wouldn't spend 45 min, more like 10 min before it would finally move onto the login screen. This happened 3 times in a row whenever I would restart. In your case, you're obviously waiting long enough!
Two days ago, I had to shut down my computer for several hours because I needed to move it. When I powered back on, the computer was mysteriously behaving normal again. So my initial answer to you would be to power off for a little while and then see what happens after you power back on. If the problem still persists, do what other MacNN members advised me to do when I posted about this problem last week:
'Chuckit' posted on 6/4/05: "Try holding in apple-V when you start up. That will make it actually print what it's doing to the screen. If it's hanging on something, you should be able to see it there."
(I never had to do this because things luckily behaved normal again after I shut down for a while and didn't trash or install anything in between start-ups.)