If you’re getting a error on your LAN connection it’s possible that your network connection is attempting 802.11 authentication on your wired network. Unfortunately, it seems that Vista/Server 2008 both attempt it before reverting. As far as I can see, it’s not causing any issues, other than irritating me with a “failed” and a red question mark.
Fortunately, it’s pretty easy to fix! The authentication is handled by the Wired AutoConfig service, so it’s just a case of disabling it.