As stated by the first rsponce, the networking interface being up is a baseline
requirement. I would then want to ask if the machine known by the other systems
within you network.
Has a naming service been established? NIS , DNS, or even /etc/hosts file entries?
IF the system is on the net, there is one other thing might be, the /etc/default/login file.
There are lines that looks like this in the file:
# If CONSOLE is set, root can only login on that device.
# Comment this line out to allow remote login by root.
#
CONSOLE=/dev/console
Comment out the CONSOLE line by adding a " #" sign in front of it, and try it again....
#CONSOLE=/dev/console
Hope this is helpful,
goldhunt