Well, first of all, this also happens in creative. I was in a game of "Villager Defense" and then suddenly, when I hear a zombie sound, my game crashes. This also happens when I shoot a flame bow in Hypixel's Bow Spleef. There is no crash report, just the new Minecraft 1.1.1 saying this:

"Game ended with bad state (exit code 134)
Ignoring visibility rule and showing launcher due to a game crash
Deleting /Users/Janice/Library/Application Support/minecraft/versions/1.6.2OF/1.6.2OF-natives-1374329914517563000"

I am not sure of Optifine, but sure it happened without optifine also. I've searched this topic, but they were from like old launchers. I NEED HELP! P.S. I've searched why my games COULD crash, and it said that if 3 java files are open, it can crash, so I thought that was the reason, but I only have Minecraft open.
THIS ALSO HAPPENS IN OTHER GAMES!