I tired to extend the 802.11g wireless network broadcast by the Linksys WRT54g. However, Airport Utility will not allow me. It only allows to "join" wireless network. Why? I will allow if I want to join an Airport Extreme just not the Linksys. The Linksys is upstairs connected to the cable modem. I want to get better 802.11g range by adding an Airport Express downstairs. Your thoughts?