I'm Mean?

Put the summary of the bug you're having here

What I expected to happen was...:
...Minecraft would have no problem loading an MCedited world with a horse spawner.

What actually happened was...:
Minecraft Crashed when ever it tried to load the chunks. Also, "Minecraft Crash Report
//You're mean!"
appears in the top of the crash report. This may be natural, first 1.6 crash for me.
Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...Use MCedit on a world to create a horse spawner.
3. ...Attempt loading the world's chunks that currently contains said spawner.
4. ...Attempting this will cause an error.