must reenable network card to connect to LAN

New Inspiron 6000 w/ broadcom network card and Windows Media Center, with all patches. I connect directly to a cable modem via an ethernet cable. I must disable, then reenable the network card to connect. The session works thereafter. Whenever I unplug and go mobile, I have to go through the same routine when I replug the ethernet cable. My old laptop senses the network as soon as the cable is plugged in. Any suggestions?