10.5.2 Server won’t pull lease from Cable Modem (anymore)

Hello all,

I have a fairly new Leopard server running at home that’s been working well for a month. It’s a Dual G5 with two Ethernet interfaces; the builtin Ethernet is attached to my LAN and a PCI Ethernet card is attached to the cable modem. The machine provides services to the LAN and acts as an internet gateway/router/firewall etc.

Last week at some point, we had an extended power outage lasting somewhere around 6 hours overnight. Every computer in my house is attached to an APC UPS, and has a USB connection to the UPS device, so when the power goes out the computer will shut down nicely if it doesn’t come back quickly. This worked just fine too, the Server shut itself down clean after several minutes.

The problem though, is that since then the Server will not lease an IP address successfully from my cable modem. When I first booted the Server again, the date was set to 1/1/1970 and it had forgotten its name (IE: In the “Sharing” pref pane). This was strange, as the computer doesn’t normally do that when powered down, or even unplugged. I tested that to make sure the internal battery hadn’t died. Seemed fine.

The cable modem is not at fault, as every other Mac in the house will still pull a lease from it just fine. I’ve tried the following things to try and convince the server to lease:
*Switched the cable modem to the Built-In Ethernet
*Replaced the PCI Ethernet card with an alternative card
*Nuked the /Library/Preferences/SystemConfiguration/NetworkPreferences.plist and preferences.plist files, then rebooted and reconfigured the interfaces
*Tried adding a DHCP Client ID, though one shouldn’t be needed

I’m about out of ideas, and the Cable modem won’t speak to any device which doesn’t have an active lease from it. Meaning, if I obtain a lease on another machine and copy the configuration over to the Server, then swap the ethernet cable, the Cable modem ignores the traffic because the MAC address doesn’t match.

I strongly suspect there’s some kind of a stale cache left behind from when the power went out, but I have no idea what to try. Any help is appreciated.