java.lang.NullPointerException: Exception in server tick loop

We have a slimeblock 8x8x8 in 14w06b and it shrinks to 6x6x6(somehow) in 14w07a and when viewed renders Black inside and soon as it come sinto view causes the server to crash
Moderator Note: It might not be caused by Slime Blocks!

---- Minecraft Crash Report ----
    // Oops.
     
    Time: 2/14/14 3:38 AM
    Description: Exception in server tick loop
     
    java.lang.NullPointerException: Exception in server tick loop
            at com.mojang.authlib.GameProfile.hashCode(GameProfile.java:90)
            at java.util.WeakHashMap.put(Unknown Source)
            at org.apache.commons.lang3.builder.ToStringStyle.register(ToStringStyle.java:191)
            at org.apache.commons.lang3.builder.ToStringStyle.appendClassName(ToStringStyle.java:1453)
            at org.apache.commons.lang3.builder.ToStringStyle.appendStart(ToStringStyle.java:378)
            at org.apache.commons.lang3.builder.ToStringBuilder.<init>(ToStringBuilder.java:263)
            at org.apache.commons.lang3.builder.ToStringBuilder.<init>(ToStringBuilder.java:226)
            at com.mojang.authlib.GameProfile.toString(GameProfile.java:97)
            at ov.d(SourceFile:102)
            at ov.a(SourceFile:93)
            at ok.c(SourceFile:130)
            at net.minecraft.server.MinecraftServer.v(SourceFile:555)
            at nb.v(SourceFile:264)
            at net.minecraft.server.MinecraftServer.u(SourceFile:471)
            at net.minecraft.server.MinecraftServer.run(SourceFile:387)
            at mr.run(SourceFile:657)
     
     
    A detailed walkthrough of the error, its code path and all known details is as follows:
    ---------------------------------------------------------------------------------------
     
    -- System Details --
    Details:
            Minecraft Version: 14w07a
            Operating System: Linux (amd64) version 2.6.32-431.1.2.0.1.el6.x86_64
            Java Version: 1.7.0_01, Oracle Corporation
            Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
            Memory: 3732572976 bytes (3559 MB) / 4116054016 bytes (3925 MB) up to 4116054016 bytes (3925 MB)
            JVM Flags: 3 total; -XX:MaxPermSize=256m -Xms4096M -Xmx4096M
            IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
            Profiler Position: N/A (disabled)
            Player Count: 3 / 40; [oe['dinidini'/235, l='world', x=840.70, y=79.20, z=6351.70], oe['ismail3214'/473, l='world', x=123.50, y=88.00, z=141.50], oe['Morpheus1101'/1795, l='world', x=-20.58, y=69.00, z=103.78]]
            Is Modded: Unknown (can't tell)
            Type: Dedicated Server (map_server.txt)