Windows 2000 VPN/firewall

I have a Windows 2000 Server set up and have configured Routing and Remote Access to allow for VPN access. I can connect and authenticate fine on the LAN by private ip address 192.168.0.10. We have a router providing NAT that allows us to connect toa public ip address from the internet and tunnel through to the 192.168.0.10. I have port 1723 open for PPTP. When I try to connect a client through the internet, I get “Error 619: the specified port is not connected” Do I need more ports open?