I have a couple SME servers that will not detect the network cards correctly unless the network cable is connected and providing a valid 'link' when the server is first powered up. If I boot these systems w/ no network cable connected, I get behaviour such as you are describing.
If you haven't tried it yet, make sure everything is connected (LAN and WAN) then shutdown and TURN OFF (power down) the SME, then turn it back on.
Once my systems have booted up I can move network cables around, reconfigure IP addresses, etc. with no problems.