Whether it's the launch of Titanfall on Microsoft's servers or something totally unrelated, Xbox Live is currently experiencing "limited" capabilities. Users may experience issues signing in, or while attempting to do any matchmaking inTitanfall and Forza 5.
Viewers of our recently concluded Titanfall livestream will have seen these issues first hand. No word yet on when this will resolve. It's just hitting the end of the work day on the East Coast, so the Titanfall servers are about to experience a crushing load.