Game crashes immediately upon loading worlds created in 14w26c.

Below is the crashlog for the original issue, I was able to reproduce this by creating another 14w26c world and switching back to 14w28a.

---- Minecraft Crash Report ----
// I just don't know what went wrong

Time: 7/10/14 5:06 AM
Description: Exception ticking world

java.lang.IllegalArgumentException: Cannot get property bcl

{name=age, clazz=class java.lang.Integer, values=[0, 1, 2, 3, 4, 5, 6, 7]}

as it does not exist!
at bbw.b(SourceFile:91)
at ayt.b(SourceFile:127)
at ayt.c(SourceFile:69)
at ary.b(SourceFile:416)
at qg.h(SourceFile:373)
at qg.c(SourceFile:199)
at net.minecraft.server.MinecraftServer.x(SourceFile:578)
at net.minecraft.server.MinecraftServer.w(SourceFile:510)
at cwg.w(SourceFile:132)
at net.minecraft.server.MinecraftServer.run(SourceFile:426)
at java.lang.Thread.run(Unknown Source)

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

– Head –
Stacktrace:
at bbw.b(SourceFile:91)
at ayt.b(SourceFile:127)
at ayt.c(SourceFile:69)
at ary.b(SourceFile:416)
at qg.h(SourceFile:373)
at qg.c(SourceFile:199)

– Affected level –
Details:
Level name: 14w26c
All players: 1 total; [qj['setback_san'/157, l='14w26c', x=43.70, y=4.00, z=229.30]]
Chunk stats: ServerChunkCache: 1334 Drop: 0
Level seed: 1342175596874193724
Level generator: ID 00 - default, ver 1. Features enabled: true
Level generator options:
Level spawn location: 244.00,64.00,256.00 - World: (244,64,256), Chunk: (at 4,4,0 in 15,16; contains blocks 240,0,256 to 255,255,271), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 1622442 game time, 2595606 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 168491 (now: false), thunder time: 68060 (now: false)
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Stacktrace:
at net.minecraft.server.MinecraftServer.x(SourceFile:578)
at net.minecraft.server.MinecraftServer.w(SourceFile:510)
at cwg.w(SourceFile:132)
at net.minecraft.server.MinecraftServer.run(SourceFile:426)
at java.lang.Thread.run(Unknown Source)

– System Details –
Details:
Minecraft Version: 14w28a
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.6.0_31, Sun Microsystems Inc.
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Sun Microsystems Inc.
Memory: 173541080 bytes (165 MB) / 550436864 bytes (524 MB) up to 954466304 bytes (910 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
IntCache: cache: 7, tcache: 0, allocated: 13, tallocated: 95
Profiler Position: N/A (disabled)
Player Count: 1 / 8; [qj['setback_san'/157, l='14w26c', x=43.70, y=4.00, z=229.30]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.