For Pacbell.net users: SBC has made a change to the authentication system. You must now add @pacbell.net to your PPPoE username to successfully log in to the system. Your short username alone will no longer work. This was apparently announced on the SBC status site, but the notice keeps disappearing. See »[Line Problem] PPPoE authentication fail since this morning??
That is why it's important to have a router. Problems like that would be minimal, especially when the router's connection wizard asks you for the complete username.