I just updated from 14w21b to 14w28a.
The Server starts up just as fine, but when i join with my char the first tick throws an exception and crashes the server.
The server is still running but all connect attempts resulting in conneciton errors.

I tried creating a new world with the same seed, this work and no error occured.

If this is a duplicat, i appologize. I couldn't find a bug with the same content.

Greating
Floopy_Doo

---- Minecraft Crash Report ----
// I blame Dinnerbone.

Time: 10.07.14 16:07
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 pd.x(SourceFile:285)
at net.minecraft.server.MinecraftServer.w(SourceFile:510)
at net.minecraft.server.MinecraftServer.run(SourceFile:426)
at java.lang.Thread.run(Thread.java:745)

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: McWeltHslu_14w10c
All players: 1 total; [qj['Floopy_Doo'/806, l='McWeltHslu_14w10c', x=-234.84, y=94.00, z=265.18]]
Chunk stats: ServerChunkCache: 625 Drop: 0
Level seed: 981696893129385575
Level generator: ID 00 - default, ver 1. Features enabled: true
Level generator options:
Level spawn location: -231.00,95.00,250.00 - World: (-231,95,250), Chunk: (at 9,5,10 in -15,15; contains blocks -240,0,240 to -225,255,255), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Level time: 230598843 game time, 142873228 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 65939 (now: false), thunder time: 72828 (now: false)
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Stacktrace:
at net.minecraft.server.MinecraftServer.x(SourceFile:578)
at pd.x(SourceFile:285)
at net.minecraft.server.MinecraftServer.w(SourceFile:510)
at net.minecraft.server.MinecraftServer.run(SourceFile:426)
at java.lang.Thread.run(Thread.java:745)

– System Details –
Details:
Minecraft Version: 14w28a
Operating System: Windows Server 2012 (amd64) version 6.2
Java Version: 1.8.0_05, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 804444592 bytes (767 MB) / 1058013184 bytes (1009 MB) up to 1058013184 bytes (1009 MB)
JVM Flags: 2 total; -Xms1024m -Xmx1024m
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
Profiler Position: N/A (disabled)
Player Count: 1 / 4; [qj['Floopy_Doo'/806, l='McWeltHslu_14w10c', x=-234.84, y=94.00, z=265.18]]
Is Modded: Unknown (can't tell)
Type: Dedicated Server (map_server.txt)