Leopard Freezes on Restart

Question

I'm having a Leopard installation problem I haven't seen discussed, so here goes.
Installation appears to go as it should (taking about an hour).
I get a screen saying installation was successful and a count-down to restart.
I click restart.
GRAY screen with Apple appears, and the little circular animated icon goes around and around for a minute or so.
Then freezes.
A two hour wait with a frozen animation produces nothing new.
I've forced a restart with the same result, several times.
Restart while holding down "c" DID get me back to the Leopard install screen, but a second attempted install failed in the same way.
I've seen a suggestion to try "archive and install". I've NOT tried that yet. Will try now and report results.
Since this is not a Blue Screen, I don't think this is the same problem others have had. I do not have Application Enhancer installed on this machine (at least not where other posts have expected it to be.)
If anyone has a fix to this I'd appreciate it. If I find one for myself I'll of course post that here as well.
This is on a MacBook Pro 15 inch, purchased new in August. 2G ram. Plenty of disk space free.
Sigh.
Charles

Answer 1

Thanks very much to chat2ian and Nicolas those were helpful responses.
Here is what seems to have solved my problem:
Force a shutdown from the frozen restart screen by holding down the power button.
Power back up while holding down the letter "c" to force boot from the cd/dvd drive.
Chose the option to "archive and install", rather than the default "update".
After a (lengthy) installation, the installer says it is done and ready to restart.
Click restart.
Hold breath, cross fingers, appeal to appropriate godesses.
After about 30 seconds of gray screen, solid blue screen with cursor appears.
(Think: Great-- progress is a blue screen of death. But wait!)
After a frightening pause, a color wheel appears, and hope returns!
Leopard starts, configuration help runs, and (in my case a least) 5 more packages are ultimately updated, followed by another restart.
This is also a bit of tense drama, but runs about as usual (perhaps a shade slower than Tiger.)
So far, all files and software are present, and life begins to look worth living again.
Nicolas: Sorry I didn't see your reply until after I'd started the "archive and install" run, so didn't get to see if Command-V would show me the same stopping point that you got.
chat2ian: I was within another try of adopting your approach and reverting to Tiger. I started this "simple" update at 9.45 and it is now 20.37.
The irony is I bought the MacBook Pro in August because I wasn't willing to go through another MS upgrade to Vista. I honestly thought this would go smoothly the first time. Silly me.
Thank you both for trying to help.
Charles