Tom has four iMacs and each one is getting an error when connecting to ethernet, and can't connect to the Internet because of a "self-assigned address." But he can connect via WiFi. Leo says to go to the Network system preference pane and make sure that Ethernet is dragged to the top. Also, make sure it's using DHCP in the settings. One thing that may be causing the error is that the computer doesn't see the ethernet cable when booting up, and then gives the self-assigned address. It could also be the router itself. And since all four computers are doing it, that leads Leo to believe it's the router. But it could also be the modem connection to the router. So make sure that the computers are connected to the router, not the modem. And if the cable modem is doing routing as well, then there are two routers competing. So one has to be put in bridge mode.