system resets on boot

[wade at ezri.org (Wade Menard)]

I got my hands on another Athlon 64 system, this one has an ECS 755-A 
mainboard that uses the SiS 755 NB and SiS 964 SB. Not my taste in 
boards, but what I was offered. I've been using the system for a few 
days with Windows XP with no apparent issues.

I installed FreeBSD on it, using an SESNAP cd from July 30. Everything 
goes as expected in sysinstall, but after reboot the system immedietly 
resets right when I would expect to see the loader messages. I've 
rechecked everything I can think of, and verified my fdisk/disklabel/mbr 
options.

Anyone have any ideas? Or am I just out of luck w/ this board?