Cable Modem Connection

I have 5 windows 2000 peer to peer network. One station is connected to the internet via cable modem. The same station connected to the rest via a second network card. I let this station to share internet connection with the rest. So the second cardwas assigned a static ip address. All stations can see each other. They can bing each other. Only the station connected to the cable can not bing its cards, or loop back. Therefore the rest of the stations can not connect to the internet. All station are assigned automatic ip addresses. Note: one card is built in. I tried different new nic cards. Please help.
thanks
hameed