Bukkit

07:09:34 [INFO] TheHoge[/127.0.0.1:54079] logged in with entity id 1796 at ([world] 76.15271743313644, 123.0
, 133.68781515492844)
07:09:34 [SEVERE] java.util.ConcurrentModificationException
07:09:34 [SEVERE]       at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
07:09:34 [SEVERE]       at java.util.ArrayList$Itr.next(Unknown Source)
07:09:34 [SEVERE]       at me.ibhh.BookShop.BookShopListener.join(BookShopListener.java:249)
07:09:34 [SEVERE]       at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
07:09:34 [SEVERE]       at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
07:09:34 [SEVERE]       at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
07:09:34 [SEVERE]       at java.lang.reflect.Method.invoke(Unknown Source)
07:09:34 [SEVERE]       at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:425)
07:09:34 [SEVERE]       at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
07:09:34 [SEVERE]       at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
07:09:34 [SEVERE]       at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
07:09:34 [SEVERE]       at net.minecraft.server.v1_5_R3.PlayerList.c(PlayerList.java:204)
07:09:34 [SEVERE]       at net.minecraft.server.v1_5_R3.PlayerList.a(PlayerList.java:100)
07:09:34 [SEVERE]       at net.minecraft.server.v1_5_R3.PendingConnection.d(PendingConnection.java:129)
07:09:34 [SEVERE]       at net.minecraft.server.v1_5_R3.PendingConnection.c(PendingConnection.java:44)
07:09:34 [SEVERE]       at net.minecraft.server.v1_5_R3.DedicatedServerConnectionThread.a(DedicatedServerCon
nectionThread.java:41)
07:09:34 [SEVERE]       at net.minecraft.server.v1_5_R3.DedicatedServerConnection.b(SourceFile:29)
07:09:34 [SEVERE]       at net.minecraft.server.v1_5_R3.MinecraftServer.r(MinecraftServer.java:581)
07:09:34 [SEVERE]       at net.minecraft.server.v1_5_R3.DedicatedServer.r(DedicatedServer.java:226)
07:09:34 [SEVERE]       at net.minecraft.server.v1_5_R3.MinecraftServer.q(MinecraftServer.java:477)
07:09:34 [SEVERE]       at net.minecraft.server.v1_5_R3.MinecraftServer.run(MinecraftServer.java:410)
07:09:34 [SEVERE]       at net.minecraft.server.v1_5_R3.ThreadServerApplication.run(SourceFile:573)
07:09:34 [INFO] [BookShop] Error: Uncatched Exeption!
07:09:35 [INFO] [BookShop] Sending issue report to ibhh.de!
07:09:35 [INFO] [BookShop] -------------------------
07:09:35 [INFO] [BookShop] Version: 5.2
07:09:35 [INFO] [BookShop] ErrorID: 3321
07:09:35 [INFO] [BookShop] Gameversion: 1.5.2-R0.2-SNAPSHOT
07:09:35 [INFO] [BookShop] Other: Player join throws error
07:09:35 [INFO] [BookShop] Message: none
07:09:35 [INFO] [BookShop] Class: BookShopListener
07:09:35 [INFO] [BookShop] -------------------------
07:09:35 [INFO] [BookShop] Message of Server: Issue already reported
07:09:35 [INFO] [BookShop] -------------------------

How often does that issue happen?

I can't remember completely since I deleted it a while back because of this error (I hate errors in console. They are so annoying) but I'm very sure there was about a 50% chance it gave this error when a player joined.
EDIT: Maybe a glitch with the default book?

@MCGamer20000: Go

You used the /giveall? Short fix: delete the temp directory

Bugfix is in progress.

I didn't use /giveall. I have no idea what my other ops do though. Either way, thanks for helping.

Did you delete the temp directory? Did it resolve your issue? Can we remove this ticket?