You'll have to have root privileges to fix this file. The easiest way to do this is to first 'cd /etc' then type 'sudo cp hostconfig hostconfig.bad' (in case we want to go backwards, we'll make a copy) then 'sudo rm hostconfig' (to get rid of the bad one), and finally, 'sudo pico hostconfig' (you'll need to enter your password on the first 'sudo'). This will put you in pico, the simplest of the command line editors. Once there, copy and paste the following text, save the change, and quit pico. I'm not sure whether you'll need to logout and/or restart, but it can't hurt.
COPY EVERYTHING BELOW THE DOTTED LINE:
--------------------------------------
##
# /etc/hostconfig
##
# This file is maintained by the system control panels
##
# Network configuration
HOSTNAME=-AUTOMATIC-
ROUTER=-AUTOMATIC-
# Services
AFPSERVER=-NO-
APPLETALK=en0
AUTHSERVER=-NO-
AUTOCONFIG=-YES-
AUTODISKMOUNT=-REMOVABLE-
AUTOMOUNT=-YES-
CONFIGSERVER=-NO-
IPFORWARDING=-NO-
MAILSERVER=-NO-
MANAGEMENTSERVER=-NO-
NETBOOTSERVER=-NO-
NISDOMAIN=-NO-
TIMESYNC=-NO-
QTSSERVER=-NO-
SSHSERVER=-NO-
WEBSERVER=-NO-
APPLETALK_HOSTNAME="My Mac"

