I was playing with golems on the new snapshot and I don't know if it's only in in this one, but 13w42b crashes whenever I spawn an iron golem and it runs around. It worked for the first couple seconds but then the game froze, like server lag freeze but I was on singleplayer. Then i reopened the world and tried flying away once the iron golem started attacking something. It lagged really bad until it completely froze and I had to restart minecraft.