NT Workstation LAN configuration

I am trying to test our FTP site from outside our Firewall. I plugged in an NT4.0 spk4 laptop, manaully assigned an IP address, Subnet, Gateway, and DNS entry. I have it plugged into the Black side of the Firewall and for some reason I am not getting out…..yet I took another laptop with WIN98 on it, did the same, and had no problems with it on the black side of the firewall. Does anyone know why my NT4.0 workstation will not work on the other side of the firewall? Is there a setting or service that must be running?

Thanks…