Thanks to everyone, who replied to my request for help in sorting out my problem playing Tanx after installing Norton Internet security. I tried everybodys suggestion but still had problems, however just by chance I think I've solved it.
I disabled my Firewall installed Tanx PC game, played Tanx in a game then closed down Tanx and enabled my Firewall, then opened Tanx again, the Firewall came up saying Tanx is trying to connect I then gave it permission and since then (keep my fingers crossed) it works, so far I've started and closed Tanx 5 times and I can still play Tanx.