Game wont initialize with MasterServer Build at home

I have used unity's unaltered Masterserver source code and built it at home.

when the game asks to Initialize... The server seem's to be doing its job with a log saying it has sent however many bytes back to the ip and port of the user but I get this error in the game counsel:

"Failed to initialize network interface. Is the listen port already in use?"

Anyways, seems the server is listening and attempting to send signals back but for some reason the users are getting it?

Funny thing is. the first time I started the game everything worked fine and nothing ever since.

of course, the game works fine when i switch the ip back to unity's test server I used for development.

anyways, this is all just running at my house with my router set to forward a port for my server machine. both the game and the server are on windows 7.

any ideas on why this might be happening would be appreciated!