I'm a total newbie, I just installed bitcoin yesterday and I have yet to generate a coin.  Last night after I installed, I asked bitcoin to generate coins and made sure it had connectivity through both my software and hardware firewalls.  Bitcoin still didn't use almost any CPU, and I saw the block number in the GUI increasing rather quickly, perhaps a few every second.  This morning my CPU is pegged (across all four cores) and the block number visible in the GUI is no longer increasing, but appears stuck at a constant value.

My newbie questions are:

Is my experience above expected behavior?

Under what conditions should the block number increase?

Should my CPU have gone up immediately after choosing "generate coins?"

I have a quad-core 2.5GHz processor, with all 4 cores active.  How long will it likely take for me to generate my first coin?  (It's been ~14 hours since I installed, but I don't know when last night the computer transitioned from no-CPU usage to full-CPU usage)

Thanks!