Looks like the same DNS problems at WON.net/Flipside.com (story) are affecting TRIBES 2 as well, as some people are having problems with the authentication servers for the game (thanks MoreGaming). Here's the comment from Dynamix' Dave Georgeson that was posted over at TribalWar:

There is a problem with the Sierra/WON/Flipside DNS. It's preventing authentication from happening.

We're trying to figure it out now.

The problems we were experiencing last night were the precursor to the total collapse of the DNS we're working through now.

This has nothing to do with the Tribes 2 code. It is a hardware issue and we're working on it.