Hi, I have Ultra 10 which used to work fine, but then started refusing 
to boot. I thought it was due to dead battery in nvram module, which is 
common for machines this old. I bought a new nvram module, set it to the 
previous host id, etc. I managed to boot the machine today a few times 
and then I started having the same problems. I doesn't boot, when I turn 
the power on and off repeatedly, sometimes it starts booting, but then I 
get the following on serial console before open boot diagnostic tests 
get a chance to complete:

Watchdog Reset

scrolling across the screen, and then if I turn power off and on, it 
doesn't even get that far, it just sits there.

Any idea what's going on here?