Put the summary of the bug you're having here
I was trying to create an amplified world ant the game crashes when it is time to generate it, almost immediately.
//tested with default settings (not amplified exclusively): it still crashes.

What I expected to happen was...:
I spawn into a newly generated world. My adventure then begins.

What actually happened was...:
when I clicked "Create new world" for the second time, the game fails to generate without difficulty/over-use to my computer.

Steps to Reproduce:
1. Launch MineCraft 1.7.2 (pre-logged in [idk if this matters])
2. Click single player.
3. Click Create New World.
4. renamed it to anything, or don't rename it at all. ( i chose "amplified! ;D" the first time it happened.
5. VOID(crashes regardless) change setting from default to AMPLIFIED setting.
7. click Create New World.
8. watch as the game crashes within seconds.
9. stare at ominous debug screen in confusion.
10. repeat.
11. as you read this, you may notice there is no step 6. sppoookyyy. seriously though, this bug is annoying. I can't play amplified at all! ;(

SIDE NOTE:
a comment in the minecraft crash report;
---- Minecraft Crash Report ----
// I just don't know what went wrong

I am a java programmer so if this isn't reproduce-able on your devices, or you just want my help; feel free to contact me. I would be happy to help Contact info: Twitter- @DefianceUnstabl, skype- DefianceUnstable, Youtube- DefianceUnstable, Minecraft Username- defiance96 (I really wish I could change this to DefianceUnstable)