System won't boot after loss of power

[Robert Fitzpatrick]

Looking for some advice on how I might be able to restore a FreeBSD 8 
system after a power issue I think. This system was remote when it 
failed many months ago and only used as backup, so I waited until I was 
in town to try and fix. Now, I have a system that gives a blinking 
cursor and will not load the initial FreeBSD boot manager. The system 
has four (4) drives, two 150GB and two 1TB drives. Each pair is using 
gmirror with root, /usr, /var and /home on the 150GB pair while my 
backup data on one slice of the TB drives.

I can use Live CD and make changes to the /etc/fstab to use the slices 
of one pair of drives and chroot to the existing system without gmirror 
and read all the data from all the partitions. This works for all drives 
updating fstab for each pair of drives.

No matter how I update the fstab file, I just get a blinking cursor 
without reaching the FreeBSD boot manager at all. How can I diagnose 
further or restore the boot process?

-- 
Robert