An exception that occurs after displaying an error about your IP address is generally caused by an inability to determine your address with the listing server (or a configuration on the individual game server, depending on the specific message). Generally this is caused by either software blocking your connection, or part of your networking configuration affecting address detection and incorrect values being reported to the server.
The FAQ entry you'll want to try for making sure your IP address is set can be found here:http://www.tribesnext.com/forum/index.php?topic=470.0
In particular, you'll want to refer to the last section of that comment. You may also want to type echo($IPv4::InetAddress);
into your console prior to updating the value if you're unsure if it is currently set.