Two of my worlds have entered a state that they are unplayable. After clicking play world, the game returns to the title screen. It then sits there for a few minutes until the RAM allocation fills up. Even with 8gb allocated, the activity monitor shows that it fills up all 8gb. The game then displays the out of ram option and must be quit and relaunched. I have attached one of the problem worlds. One is a redstone/snapshot world and the other is a survival world.
MC-25523
Minecraft memory leak
Resolved
Invalid
0
That world is corrupt.
Probably you broke it as you have edited with MCEdit.
You may have here http://www.minecraftforum.net/topic/137381-official-corrupted-save-recovery-thread/ your world repaired.