Minecraft Forums

---- Minecraft Crash Report ----
// Why did you do that?

Time: 9/17/15 8:11 PM
Description: Exception in server tick loop

java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextNode(HashMap.java:1429)
at java.util.HashMap$KeyIterator.next(HashMap.java:1453)
at net.minecraft.entity.EntityTracker.func_72788_a(EntityTracker.java:269)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:648)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:547)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:186)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:427)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685)

A detailed walkthrough of the error, its code path and all known details is as follows:
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-- System Details --
Details:
Minecraft Version: 1.7.10
Operating System: Windows 8.1 (amd64) version 6.3
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 319169032 bytes (304 MB) / 834740224 bytes (796 MB) up to 1060372480 bytes (1011 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
FML: MCP v9.05 FML v7.10.99.99 Minecraft Forge 10.13.4.1448 Optifine OptiFine_1.7.10_HD_B7 26 mods loaded, 26 mods active
States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored
UCHIJAAAA mcp{9.05} [Minecraft Coder Pack] (minecraft.jar)
UCHIJAAAA FML{7.10.99.99} [Forge Mod Loader] (forge-1.7.10-10.13.4.1448-1.7.10.jar)
UCHIJAAAA Forge{10.13.4.1448} [Minecraft Forge] (forge-1.7.10-10.13.4.1448-1.7.10.jar)
UCHIJAAAA AM2-Preloader{0.0.2} [AMCore] (minecraft.jar)
UCHIJAAAA CodeChickenCore{1.0.2.11} [CodeChicken Core] (minecraft.jar)
UCHIJAAAA NotEnoughItems{1.0.2.15} [Not Enough Items] (NotEnoughItems-1.7.10-1.0.2.15-universal.jar)
UCHIJAAAA AnimationAPI{1.2.4} [AnimationAPI] (AnimationAPI-1.7.10-1.2.4.jar)
UCHIJAAAA arsmagica2{1.4.0.008} [Ars Magica 2] (1.7.10_AM2-1.4.0.008.jar)
UCHIJAAAA DamageIndicatorsMod{3.2.0} [Damage Indicators] ([1.7.10]DamageIndicatorsMod-3.2.0.jar)
UCHIJAAAA bspkrsCore{6.16} [bspkrsCore] ([1.7.10]bspkrsCore-universal-6.16.jar)
UCHIJAAAA Treecapitator{1.7.10} [Treecapitator] ([1.7.10]Treecapitator-universal-2.0.4.jar)
UCHIJAAAA Backpack{2.0.1} [Backpack] (backpack-2.0.1-1.7.x.jar)
UCHIJAAAA BiblioCraft{1.10.4} [BiblioCraft] (BiblioCraft[v1.10.4][MC1.7.10].jar)
UCHIJAAAA craftguide{1.6.8.1} [CraftGuide] (CraftGuide-1.6.8.1.zip)
UCHIJAAAA MoCreatures{6.3.1} [DrZhark's Mo'Creatures Mod] (DrZharks MoCreatures Mod v6.3.1 (1).zip)
UCHIJAAAA eplus{3.0.2-d} [Enchanting Plus] (EnchantingPlus-1.7.10-3.0.2-d.jar)
UCHIJAAAA inventorytweaks{1.58-147-645ca10} [Inventory Tweaks] (Inventory-Tweaks-Mod-1.7.10 (2).jar)
UCHIJAAAA journeymap{@[email protected]} [JourneyMap] (journeymap-1.7.10-5.1.0-unlimited.jar)
UCHIJAAAA RadixCore{2.0.2} [RadixCore] (RadixCore-2.0.2-1.7.10-universal.jar)
UCHIJAAAA MCA{1.7.10-5.0.7.1} [Minecraft Comes Alive] (MCA-1.7.10-5.0.7.1-universal.jar)
UCHIJAAAA cfm{3.4.7} [§9MrCrayfish's Furniture Mod] (MrCrayfishFurnitureModv3.4.7(1.7.10).jar)
UCHIJAAAA DP_SimpleFlight{0.8} [Simple Flight] (Simple-Flight-Mod-1.7.10.jar)
UCHIJAAAA Baubles{1.0.1.10} [Baubles] (Baubles-1.7.10-1.0.1.10.jar)
UCHIJAAAA Thaumcraft{4.2.3.5} [Thaumcraft] (Thaumcraft-1.7.10-4.2.3.5.jar)
UCHIJAAAA TwilightForest{2.3.3} [The Twilight Forest] (twilightforest-1.7.10-2.3.3.jar)
UCHIJAAAA witchery{0.24.1} [Witchery] (witchery-1.7.10-0.24.1.jar)
Profiler Position: N/A (disabled)
Vec3 Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Player Count: 1 / 8; [EntityPlayerMP['NegroChan'/236, l='Enchanted Wonderland', x=1188.20, y=67.00, z=-344.19]]
Type: Integrated Server (map_client.txt)
Is Modded: Definitely; Client brand changed to 'fml,forge'

Do read the pages where you get these mods from... Mo creatures requires the custom mob spawner mod. You can download that from the Mo creatures thread.