Other then stating the unknown network, are you able to establish a connection? Just curious, is your SSID disabled? If so try enabling it and then checking. It's the same on my home network...I've disabled the SSID, which just stops the broadcast of your network name, and all my wireless devices (laptops) have an extra network connection at the bottom of the list named unknown network. As soon as I enable it...the unknown network disappears. I always keep my SSID turned off...just another form of security for me.
I think you have to actually connect to the network through the device (XBox) network connection panel in the settings area...like I have to do with my Wii. It can be a lengthy process for some devices.