The game crashes while trying to load a single player game in 1.6.1

I open Minecraft 1.6.1
I click on Single Player
All of my worlds load just fine except for one.
When I try to load that one save the game crashes immediately.

Here is the error log dump:

---- Minecraft Crash Report ----
// Ouch. That hurt :(

Time: 7/6/13 5:04 PM
Description: Exception in server tick loop

java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
	at java.util.HashMap$ValueIterator.next(Unknown Source)
	at aii.a(SourceFile:73)
	at aeo.a(SourceFile:425)
	at jo.a(SourceFile:168)
	at adm.a(SourceFile:732)
	at jo.c(SourceFile:105)
	at jn.<init>(SourceFile:29)
	at jm.a(SourceFile:208)
	at jm.a(SourceFile:240)
	at hk.a(SourceFile:138)
	at hk.c(SourceFile:185)
	at hk.a(SourceFile:82)
	at bkr.b(SourceFile:73)
	at net.minecraft.server.MinecraftServer.t(SourceFile:488)
	at net.minecraft.server.MinecraftServer.s(SourceFile:405)
	at bko.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:339)
	at hf.run(SourceFile:582)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- System Details --
Details:
	Minecraft Version: 1.6.1
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_10, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 111751264 bytes (106 MB) / 194510848 bytes (185 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 1521 (85176 bytes; 0 MB) allocated, 1521 (85176 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 1, tallocated: 63
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 179 (10024 bytes; 0 MB) allocated, 179 (10024 bytes; 0 MB) used
	Player Count: 1 / 8; [js['Go_Geeta'/153, l='MAIN', x=-788.28, y=64.70, z=2.48]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.