Customised superflat Freezes and crashes unclosable

I Was trying Out Superflat for a map it was

it should load normal

I don't get what happened

I don't get why it freezes and says it crashes In the console without a crash report tab and minecraft is still open and un-closable
Layer 1 obsidian: 49
Layer 2 stone: 1
Note: minecraft:# doesn't change anything Note: I try 1.7.2 it worked fine probably due to the new Minecraft:#s And without
Personaly I like the old way but then again so do some people and so don't others so keep it 1.7s way