I'm not so SMRT.

The problem I had was simply mismatched version of Nerf... my server was 1.2 and I was running 1.2 CP on my desktop.

Soon as I switched my desktop to standard 1.2 it all worked a treat.

I did have to modify my Nerf.INI to change the master server still but it works, and best of all I can play again easily on my server.