check you have a line like "127.0.0.1 localhost localhost.localdomain" in your /etc/hosts file, also check you have a proper loopback interface configured, in /etc/sysconfig/network-scripts/ifcfg-lo mine says
Code:
DEVICE=lo
IPADDR=127.0.0.1
NETMASK=255.0.0.0
NETWORK=127.0.0.0
# If you're having problems with gated making 127.0.0.0/8 a martian,
# you can change this to something else (255.255.255.255, for example)
BROADCAST=127.255.255.255
ONBOOT=yes
NAME=loopback
also, try bringing up the interface from the command line directly (ifup lo), you should be able to get more information out f it that way. that's if it actually is the lo that's giving you your problem