What is causing this?

After some period of time (30 minutes to an 1 hour) the server just crashes saying:

Code:

27.01 10:35:27 [Server] SEVERE This crash report has been saved to: \.\crash-reports\crash-2013-01-27_10.35.27-server.txt
27.01 10:35:27 [Server] INFO ... 4 more
27.01 10:35:27 [Server] INFO at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:580)
27.01 10:35:27 [Server] INFO at net.minecraft.server.v1_4_R1.WorldServer.tickEntities(WorldServer.java:445)
27.01 10:35:27 [Server] INFO at net.minecraft.server.v1_4_R1.World.tickEntities(World.java:1228)
27.01 10:35:27 [Server] INFO at java.util.ArrayList$Itr.next(Unknown Source)
27.01 10:35:27 [Server] INFO at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
27.01 10:35:27 [Server] INFO Caused by: java.util.ConcurrentModificationException
27.01 10:35:27 [Server] INFO at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849)
27.01 10:35:27 [Server] INFO at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:427)
27.01 10:35:27 [Server] INFO at net.minecraft.server.v1_4_R1.MinecraftServer.q(MinecraftServer.java:494)
27.01 10:35:27 [Server] INFO at net.minecraft.server.v1_4_R1.DedicatedServer.r(DedicatedServer.java:224)
27.01 10:35:27 [Server] INFO at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:584)
27.01 10:35:27 [Server] INFO net.minecraft.server.v1_4_R1.ReportedException: Exception ticking world entities
27.01 10:35:27 [Server] SEVERE Encountered an unexpected exception ReportedException
27.01 10:35:27 [Server] SEVERE ... 4 more
27.01 10:35:27 [Server] SEVERE at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:580)
27.01 10:35:27 [Server] SEVERE at net.minecraft.server.v1_4_R1.WorldServer.tickEntities(WorldServer.java:445)
27.01 10:35:27 [Server] SEVERE at net.minecraft.server.v1_4_R1.World.tickEntities(World.java:1228)
27.01 10:35:27 [Server] SEVERE at java.util.ArrayList$Itr.next(Unknown Source)
27.01 10:35:27 [Server] SEVERE at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
27.01 10:35:27 [Server] SEVERE Caused by: java.util.ConcurrentModificationException
27.01 10:35:27 [Server] SEVERE at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849)
27.01 10:35:27 [Server] SEVERE at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:427)
27.01 10:35:27 [Server] SEVERE at net.minecraft.server.v1_4_R1.MinecraftServer.q(MinecraftServer.java:494)
27.01 10:35:27 [Server] SEVERE at net.minecraft.server.v1_4_R1.DedicatedServer.r(DedicatedServer.java:224)
27.01 10:35:27 [Server] SEVERE at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:584)
27.01 10:35:27 [Server] SEVERE net.minecraft.server.v1_4_R1.ReportedException: Exception ticking world entities

I've removed all my plugins and started testing them by uploading 1 at a time. I installed the essentials suite and the error started occuring. i thought i found the problem, i then remove the essentials plugins (Chat, Core, spawn) and the problem still occurs.

My plugins that are installed at the moment: (7): SpawnPoints, WorldEdit, PermissionsEx, Modifyworld, Announcer, WorldGuard, Buycraft

 

Try reloading the server?

 

I've restarted the MC server many times..

 

Is all of your plugins up to date?
Try removing all of the plugins start your server up, and if the error doesnt come up its one of your plugins

 

Show us what's there.

 

On a side note:
Be sure not to use "/reload" unless you are using a recent development build of CraftBukkit (roughly CB2620 or higher), or a CB version from more than five months ago, because unless i am mistaken a bug has been around since then:
https://github.com/Bukkit/CraftBukkit/commit/eea7fc2067d7d7fc08c72414b662d0a065495264

I also discourage using "/reload" with players online (including admins...), because of the load order of plugins is not certain and the permissions plugin not being present while checking permissions might have unwanted effects.

(Heavily edited.)

 

I never use /reload. Ive heard alot of bad things about it and it breaks my PEX so i just have to restart.

 

If

this happends without any plugins then, it's a chunk error. However it might be SpawnPoints, Worldedit, MonitorTPS or Enjin MInecraft, one of them might be outdated, or one is interfering with other.

 

I think its Spawnpoints, let me do a bit more testing.

 

My creative server has this too, I think that is a Bukkit bug, happens after #02621

 

This happened to me, and it was a plugin that I screwed up a config file on. I believe it was dynmap. Check any config files you have changed recently.