Windows Server with 2 LAN Cards

I have a Windows Server 2K3 setup with 2 LAN Cards one connected to the local network assigned an IP through DHCP and one connected directly into our router which is assigned one of our static IP addresses provided by our ISP. I am trying to configure the server as a Web Server but have no luck connecting to the web server from outside the local network unless the network adapter connected to the local network is unplugged. Any Ideas ???