@nfw I recently bought new hardware (64bit) and when attempted to install pfsense on it i had EXACTLY the same issues you did (bootloop). I tried to troubleshoot it the same way you did but no luck.
NanoBSD on a CF card would boot fine but had other issues like not being able to run snort or suricata and…!
Frustrated and a little sad for my misfortune i decided to use it as an extra GNU/Linux-desktop for experimenting. It served well that purpose until this noon when i decided to give the 2.2.4 a go!
BINGO!!! installed just fine and is now my new pfs-box!
I did Uncheck the 'packet mode' box during bootblock installation but i don't know if that was necessary. I didn't bother reinstalling just to check it.
SATA SSD 60gb full partition from Muskin.
I am planning to make a new thread about the hardware i used. Very... VERY... Happy with the result
Regards!