MOSXS keeps forgetting its IP address

My MOSXS machine has had the OS reinstalled several times now, (which I'm sure you can imagine requires a load of time and energy) because it forgets (?) what its IP address is, and there doesn't seem to be any way to set it again without running the setup program that runs post install. If I use ifconfig to alias the ethernet port to some IP it seems to grab the IP temporarily, but I can't seem to get the link status to become "Active" - no matter how many times I tell it to "up" it stays "Inactive". Also, as soon as the machine needs to be rebooted it forgets its IP again and the whole process gets repeated. Any ideas would really help. Here's my setup I'm working with right now as a test setup for the real thing when my Xserve comes in a few weeks: - 1 snow iMac running MOSXS 10.2 - 1 tray-load blueberry iMac NetBoot client - 1 snow iMac NetBoot client - physically segregated private network