#1 - March 19, 2012, 7:50 a.m.
After defeating the skeleton king, I attempted to join a public game.
Players who kill the Skeleton King cannot queue for Public Games for the quest "Reign of the Black King".
Workaround - Create a new game on the beginning of the "Reign of the Black King" quest and exit that game. You should be able to queue for Public Games again.