java.util.ConcurrentModificationException
    at java.util.HashMap$HashIterator.nextNode(HashMap.java:1437)
    at java.util.HashMap$KeyIterator.next(HashMap.java:1461)
    at net.minecraft.server.management.PlayerChunkMap.func_72693_b(SourceFile:114)
    at net.minecraft.world.WorldServer.func_72835_b(WorldServer.java:227)
    at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:756)
    at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:397)
    at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:668)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526)
    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 --
Thread: Server thread
Stacktrace:
    at java.util.HashMap$HashIterator.nextNode(HashMap.java:1437)
    at java.util.HashMap$KeyIterator.next(HashMap.java:1461)
    at net.minecraft.server.management.PlayerChunkMap.func_72693_b(SourceFile:114)
    at net.minecraft.world.WorldServer.func_72835_b(WorldServer.java:227)

-- Affected level --
Details:
    Level name: DIM100
    All players: 9 total; [EntityPlayerMP['Miawou'/5038, l='DIM100', x=681.64, y=70.00, z=-2602.16], EntityPlayerMP['_Cilo_'/1135, l='DIM100', x=-322.05, y=74.20, z=-3127.35], EntityPlayerMP['Syphin777'/275383, l='DIM100', x=2787.38, y=135.00, z=-1360.30], EntityPlayerMP['WarShepherd'/836975, l='DIM100', x=-1241.64, y=156.00, z=2814.24], EntityPlayerMP['TinySmalls'/836940, l='DIM100', x=1319.41, y=96.00, z=1155.41], EntityPlayerMP['dragon87tamer'/859023, l='DIM100', x=1318.90, y=72.00, z=1197.70], EntityPlayerMP['Cubelex_YT'/920001, l='DIM100', x=-262.60, y=77.42, z=-2544.81], EntityPlayerMP['BookerTheGeek'/58292, l='DIM100', x=-313.24, y=73.46, z=-3130.92], EntityPlayerMP['Regulator_1A'/1070755, l='DIM100', x=83.50, y=63.00, z=-2664.50]]
    Chunk stats: ServerChunkCache: 1070 Drop: 0
    Level seed: -1187909389772010715
    Level generator: ID 00 - default, ver 1. Features enabled: true
    Level generator options: {"coordinateScale":175.0,"heightScale":75.0,"lowerLimitScale":512.0,"upperLimitScale":512.0,"depthNoiseScaleX":200.0,"depthNoiseScaleZ":200.0,"depthNoiseScaleExponent":0.5,"mainNoiseScaleX":165.0,"mainNoiseScaleY":106.61267,"mainNoiseScaleZ":165.0,"baseSize":8.267606,"stretchY":13.387607,"biomeDepthWeight":1.2,"biomeDepthOffset":0.2,"biomeScaleWeight":3.4084506,"biomeScaleOffset":0.0,"seaLevel":63,"useCaves":false,"useDungeons":false,"dungeonChance":7,"useStrongholds":false,"useVillages":true,"useMineShafts":true,"useTemples":true,"useMonuments":true,"useRavines":true,"useWaterLakes":true,"waterLakeChance":49,"useLavaLakes":true,"lavaLakeChance":80,"useLavaOceans":false,"fixedBiome":-1,"biomeSize":4,"riverSize":5,"dirtCount":0,"gravelCount":0,"graniteCount":0,"dioriteCount":0,"andesiteCount":0,"coalCount":0,"ironCount":0,"goldCount":0,"redstoneCount":0,"diamondCount":0,"lapisCount":0}
    Level spawn location: World: (0,88,0), Chunk: (at 0,5,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
    Level time: 71399176 game time, 71399176 day time
    Level dimension: 0
    Level storage version: 0x04ABD - Anvil
    Level weather: Rain time: 69085 (now: false), thunder time: 86476 (now: false)
    Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: true

-- Sponge PhaseTracker --
Details:
    Phase Stack: [Empty stack]
Stacktrace:
    at net.minecraft.server.MinecraftServer.handler$onCrashReport$zjo000(MinecraftServer.java:3975)
    at net.minecraft.server.MinecraftServer.func_71230_b(MinecraftServer.java:889)
    at net.minecraft.server.dedicated.DedicatedServer.func_71230_b(DedicatedServer.java:371)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:554)
    at java.lang.Thread.run(Thread.java:745)