My guess is that HAL and UDEV saved information on eth0 including the MAC address (persistant network device naming). The MAC differs on the second host so the system created a new ifcfg-<dev> for it. This comes in handy if you have a pcmcia NIC device. You could plug in one card for work and another one for home and you don't need to reconfigure the network setup, just change NIC cards.
Also check for these files:
/etc/udev/rules.d/70-persistent-net.rules
/etc/udev/rules.d/75-persistent-net-generator.rules
Code:
# This file was automatically generated by the /lib/udev/write_net_rules
# program run by the persistent-net-generator.rules rules file.
#
# You can modify it, as long as you keep each rule on a single line.
# PCI device 0x10ec:0x8139 (8139too)
SUBSYSTEM=="net", DRIVERS=="?*", ATTR{address}=="00:0f:b0:0c:ef:ab", NAME="eth0"
# PCI device 0x14e4:0x4320 (bcm43xx)
SUBSYSTEM=="net", DRIVERS=="?*", ATTR{address}=="00:90:4b:92:71:a1", NAME="eth1"
# PCI device 0x1737:0xab09 (tulip)
SUBSYSTEM=="net", DRIVERS=="?*", ATTR{address}=="00:04:5a:9d:d6:e8", NAME="eth2"
jschiwal@hpamd64:/usr/src/linux/fs/cifs>
In this file, eth0 refers to my built in nic device (on laptop) that failed on me. The second is the built in wireless interface. The third is a PCMCIA card that I normally use.
The easiest way to deal with it may be to run your network configuration program and delete the interfaces and start over.
Make sure you change the hostname so that it is unique. If you have static IPs, the two hosts must have different IPs as well.