Put the summary of the bug you're having here

What I expected to happen was...:
For the world to load

What actually happened was...:
MineCraft froze then cut to the main menu for about 20 seconds, then the game crashed with a code in the launcher, the code it as follows:

---- Minecraft Crash Report ----
// Why is it breaking

Time: 11/9/13 4:59 PM
Description: Ticking entity

java.lang.OutOfMemoryError: Java heap space
at atd.a(SourceFile:27)
at abw.a(SourceFile:781)
at abw.a(SourceFile:689)
at abw.a(SourceFile:1579)
at abr.a(SourceFile:114)
at js.a(SourceFile:668)
at abw.a(SourceFile:1555)
at tc.d(SourceFile:85)
at tc.l_(SourceFile:75)
at abw.a(SourceFile:1349)
at js.a(SourceFile:479)
at abw.g(SourceFile:1327)
at abw.h(SourceFile:1234)
at js.h(SourceFile:364)
at net.minecraft.server.MinecraftServer.t(SourceFile:471)
at net.minecraft.server.MinecraftServer.s(SourceFile:406)
at bkz.s(SourceFile:124)
at net.minecraft.server.MinecraftServer.run(SourceFile:340)
at hi.run(SourceFile:583)

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

– Head –
Stacktrace:
at atd.a(SourceFile:27)
at abw.a(SourceFile:781)
at abw.a(SourceFile:689)
at abw.a(SourceFile:1579)
at abr.a(SourceFile:114)
at js.a(SourceFile:668)
at abw.a(SourceFile:1555)
at tc.d(SourceFile:85)
at tc.l_(SourceFile:75)
at abw.a(SourceFile:1349)
at js.a(SourceFile:479)
at abw.g(SourceFile:1327)

– Entity being ticked –
Details:
Entity Type: PrimedTnt (tc)
Entity ID: 847
Entity Name: Block of TNT
Entity's Exact location: 154.93, 12.06, 1100.27
Entity's Block location: World: (154,12,1100), Chunk: (at 10,0,12 in 9,68; contains blocks 144,0,1088 to 159,255,1103), Region: (0,2; contains chunks 0,64 to 31,95, blocks 0,0,1024 to 511,255,1535)
Entity's Momentum: -1.53, -0.19, 0.74
Stacktrace:
at abw.h(SourceFile:1234)
at js.h(SourceFile:364)

– Affected level –
Details:
Level name: parkour
All players: 0 total; []
Chunk stats: ServerChunkCache: 701 Drop: 0
Level seed: -6797365821394380595
Level generator: ID 01 - flat, ver 0. Features enabled: true
Level generator options:
Level spawn location: World: (256,6,962), Chunk: (at 0,0,2 in 16,60; contains blocks 256,0,960 to 271,255,975), Region: (0,1; contains chunks 0,32 to 31,63, blocks 0,0,512 to 511,255,1023)
Level time: 366778 game time, 374349 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 44675 (now: false), thunder time: 87770 (now: false)
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
at net.minecraft.server.MinecraftServer.t(SourceFile:471)
at net.minecraft.server.MinecraftServer.s(SourceFile:406)
at bkz.s(SourceFile:124)
at net.minecraft.server.MinecraftServer.run(SourceFile:340)
at hi.run(SourceFile:583)

– System Details –
Details:
Minecraft Version: 1.6.4
Operating System: Windows Vista (x86) version 6.0
Java Version: 1.7.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
Memory: 9596784 bytes (9 MB) / 518979584 bytes (494 MB) up to 518979584 bytes (494 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
AABB Pool Size: 6418 (359408 bytes; 0 MB) allocated, 6418 (359408 bytes; 0 MB) used
Suspicious classes: No suspicious classes found.
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Profiler Position: N/A (disabled)
Vec3 Pool Size: 7731267 (432950952 bytes; 412 MB) allocated, 7731267 (432950952 bytes; 412 MB) used
Player Count: 0 / 8; []
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.

Steps to Reproduce:
1. Load file like normal in the minecraft single player menu
None more