Server error message

Hey guys ...ahh
I have some problems on my Server's error message
I don't know how to solve it

First time
2011-11-02 09:13:15 [WARNING] Task of 'NoLagg' generated an exception
java.util.ConcurrentModificationException
at java.util.WeakHashMap$HashIterator.nextEntry(Unknown Source)
at java.util.WeakHashMap$KeyIterator.next(Unknown Source)
at java.util.AbstractCollection.toArray(Unknown Source)
at com.bergerkiller.bukkit.nolagg.ChunkHandler.cleanUp(ChunkHandler.java:124)
at com.bergerkiller.bukkit.nolagg.NoLagg$2.run(NoLagg.java:134)
at org.bukkit.craftbukkit.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:137)
at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:441)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:374)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:417)
2011-11-02 09:16:03 [INFO] SOT_Nebula: Giving SOT_Nebula some 50 (TORCH)
2011-11-02 09:17:03 [INFO] SOT_Nebula: Giving SOT_Nebula some 50 (TORCH)
2011-11-02 09:18:19 [SEVERE] java.util.ConcurrentModificationException
2011-11-02 09:18:19 [SEVERE] at java.util.AbstractList$Itr.checkForComodification(Unknown Source)
2011-11-02 09:18:19 [SEVERE] at java.util.AbstractList$Itr.next(Unknown Source)
2011-11-02 09:18:19 [SEVERE] at java.util.AbstractCollection.removeAll(Unknown Source)
2011-11-02 09:18:19 [SEVERE] at net.minecraft.server.World.tickEntities(World.java:1129)
2011-11-02 09:18:19 [SEVERE] at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:467)
2011-11-02 09:18:19 [SEVERE] at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:374)
2011-11-02 09:18:19 [SEVERE] at net.minecraft.server.ThreadServerApplication.run(SourceFile:417)
2011-11-02 09:18:19 [SEVERE] Unexpected exception
java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification(Unknown Source)
at java.util.AbstractList$Itr.next(Unknown Source)
at java.util.AbstractCollection.removeAll(Unknown Source)
at net.minecraft.server.World.tickEntities(World.java:1129)
at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:467)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:374)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:417)
(↑I delete NoLagg already）

Second

2011-11-02 10:45:57 [SEVERE] java.util.ConcurrentModificationException
2011-11-02 10:45:59 [SEVERE] at java.util.AbstractList$Itr.checkForComodification(Unknown Source)
2011-11-02 10:45:59 [SEVERE] at java.util.AbstractList$Itr.remove(Unknown Source)
2011-11-02 10:45:59 [SEVERE] at java.util.AbstractCollection.removeAll(Unknown Source)
2011-11-02 10:45:59 [SEVERE] at net.minecraft.server.World.tickEntities(World.java:1129)
2011-11-02 10:45:59 [SEVERE] at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:467)
2011-11-02 10:45:59 [SEVERE] at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:374)
2011-11-02 10:45:59 [SEVERE] at net.minecraft.server.ThreadServerApplication.run(SourceFile:417)
2011-11-02 10:45:59 [SEVERE] Unexpected exception
java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification(Unknown Source)
at java.util.AbstractList$Itr.remove(Unknown Source)
at java.util.AbstractCollection.removeAll(Unknown Source)
at net.minecraft.server.World.tickEntities(World.java:1129)
at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:467)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:374)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:417)
2011-11-02 11:13:25 [INFO] Stopping server


and I have some plugins like it when I type stop on console

2011-11-02 09:26:32 [SEVERE] Error occurred (in the plugin loader) while disabling Showcase v0.7.7.11 (Is it up to date?): null
java.lang.NullPointerException
at java.lang.Class.isAssignableFrom(Native Method)
at org.bukkit.plugin.java.JavaPluginLoader.removeClass(JavaPluginLoader.java:245)
at org.bukkit.plugin.java.JavaPluginLoader.disablePlugin(JavaPluginLoader.java:992)
at org.bukkit.plugin.SimplePluginManager.disablePlugin(SimplePluginManager.java:296)
at org.bukkit.plugin.SimplePluginManager.disablePlugins(SimplePluginManager.java:289)
at org.bukkit.craftbukkit.CraftServer.disablePlugins(CraftServer.java:166)
at net.minecraft.server.MinecraftServer.stop(MinecraftServer.java:325)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:404)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:417)

Want somebody help me plz

by the way:
thoes are my plugins:
AdminCMD
AntiCreeper
AuthMe
ChestShop
GreativeGates
CreatureBox
DeamSpace
dynmap
EasyRaffle
GravelClay
GriefAlert
iConomy
Jobs
Lockette
mcMMO
MobBounty
MultiWorld
NarrowtuxLib
Permissions
Ptweaks
ShowCase
WorldEdit
xLevel
NoEnderman
Register
Seats

 

Yeah, I had that issue too.

You just have to hard shut it down and the restart it.

 

Bug in the plugin "NoLagg" -> report it to the author.

Is this really the full error message? Nothing before? If so: Is your server up to date? If so: Bug in bukkit, report it!

Bug in the plugin "Showcase" -> Report it to the author!

For the reports: Always give the author(s) the full error log.