The Marathon Server Slam is off to a quick start, with impressive player numbers on Steam. Meanwhile, Bungie has acknowledged complaints around the UI and PvP frequency.
If you've downloaded the most recent GeForce 595.59 WHQL Game Ready driver, you'll want to roll back to 591.86 instead, using ...
Bungie is working on a real fix, but for now, try this.
Marathon's mouse bug is driving PC players up the wall. Here's what's causing it and how to fix it before your next run.