When a system is running in trusted mode, even the root account can be locked out to network access. To unlock it simply log in as root on the console. If not run modprpw -k root. To take a system out of trusted mode run sam or

/usr/sbin/audsys -f
/usr/lbin/tsconvert -r

and to re-trust it sam and enter trusted mode. The option to 'untrust' a system is in the action menu on most of the applets in the sam area 'Auditing and Security'