Crash on loading converted level

Since I imagine someone would point out that I'm running java 1.8, I retested with 1.7:

---- Minecraft Crash Report ----
// Oh - I know what I did wrong!

Time: 31/01/14 01:51
Description: Unexpected error

java.lang.NullPointerException: Unexpected error
	at bpv.a(SourceFile:540)
	at bpv.b(SourceFile:514)
	at bpq.b(SourceFile:680)
	at bpq.a(SourceFile:1236)
	at bpq.b(SourceFile:923)
	at bcf.ag(SourceFile:803)
	at bcf.f(SourceFile:730)
	at net.minecraft.client.main.Main.main(SourceFile:154)


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

-- Head --
Stacktrace:
	at bpv.a(SourceFile:540)
	at bpv.b(SourceFile:514)
	at bpq.b(SourceFile:680)
	at bpq.a(SourceFile:1236)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bpg['DwarfStonebeard'/3, l='MpServer', x=85.70, y=65.62, z=49.79]]
	Chunk stats: MultiplayerChunkCache: 45, 45
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: 80.00,4.00,65.00 - World: (80,4,65), Chunk: (at 0,0,1 in 5,4; contains blocks 80,0,64 to 95,255,79), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 79482 game time, 79482 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: Game mode: spectator (ID 3). Hardcore: false. Cheats: false
	Forced entities: 4 total; [xp['item.item.string'/0, l='MpServer', x=86.88, y=64.13, z=49.78], xp['item.item.spiderEye'/1, l='MpServer', x=86.88, y=64.13, z=50.19], yu['Spider'/2, l='MpServer', x=85.72, y=64.00, z=49.81], bpg['DwarfStonebeard'/3, l='MpServer', x=85.70, y=65.62, z=49.79]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at bne.a(SourceFile:298)
	at bcf.b(SourceFile:2010)
	at bcf.f(SourceFile:744)
	at net.minecraft.client.main.Main.main(SourceFile:154)

-- System Details --
Details:
	Minecraft Version: 14w05a
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_45, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 381105416 bytes (363 MB) / 515375104 bytes (491 MB) up to 515375104 bytes (491 MB)
	JVM Flags: 3 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xms512M -Xmx512M
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Launched Version: 14w05a
	LWJGL: 2.9.1
	OpenGL: AMD Radeon HD 6800 Series GL version 4.3.12618 Compatibility Profile Context 13.251.0.0, ATI Technologies Inc.
	GL Caps: Using GL 1.3 multitexturing.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Anisotropic filtering is supported and maximum anisotropy is 16.
Shaders are available because OpenGL 2.1 is supported.

	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Packs: []
	Current Language: English (UK)
	Profiler Position: N/A (disabled)
	Anisotropic Filtering: Off (1)