Not that we've ever run across an invincible, burning Witch, but we'd say it's probably a great thing that Valve decided to fix that particular bug in Left 4 Dead 2. You see, apparently there's a glitch that allows Witches to become invincible if set on fire, the upshot of this being that the Witch is both invincible and on fire. Sound scary? You bet your ass it is. The patch also fixes a bug that prevented the launch of the game on certain machines. Yet another tweak fixes a bug where "bots would not shoot at Jockeys and Chargers while approaching to save a teammate." Yeah, that one seems kind of important too.