random reboots on 5.3 with securelevel 1/2

[J.D. Bronson]

I am at a loss on this one..

If I set securelevel at 1 or 2, the 5.3-REL machine will randomly reboot. 
No logs - nothing on the console...just as if someone hit reboot.

No one logged in during this time either. I removed WAN access from this 
box as well.

As long as I run the default level (-1) - I never see this machine reboot.

All it does is run postfix/bind...not X or anything. It is a headless machine.

Ideas? things to check?

I can run at default level for weeks, but cannot run at any secure level 
for more than a few hours.

  -JDB