ConcurrentModificationException Error

[Eliminator]

Sometimes my server just closes with a "java.util.ConcurrentModificationException" error.

 

I know its not a problem with Forge, but with my mods installed (Two are conflicting?).

 

Any way I was wondering if anyone has gotten this error before and what generally causes it.

 

MC error report:

Description: Ticking entity

java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:839)
at java.util.HashMap$KeyIterator.next(HashMap.java:874)
at net.minecraft.entity.EntityLivingBase.func_70679_bo(EntityLivingBase.java:521)
at net.minecraft.entity.EntityLivingBase.func_70030_z(EntityLivingBase.java:293)
at net.minecraft.entity.EntityLiving.func_70030_z(EntityLiving.java:157)
at net.minecraft.entity.Entity.func_70071_h_(Entity.java:318)
at net.minecraft.entity.EntityLivingBase.func_70071_h_(EntityLivingBase.java:1559)
at net.minecraft.entity.EntityLiving.func_70071_h_(EntityLiving.java:206)
at net.minecraft.entity.monster.EntityMob.func_70071_h_(SourceFile:30)
at net.minecraft.world.World.func_72866_a(World.java:2043)
at net.minecraft.world.WorldServer.func_72866_a(WorldServer.java:648)
at net.minecraft.world.World.func_72870_g(World.java:2007)
at net.minecraft.world.World.func_72939_s(World.java:1860)
at net.minecraft.world.WorldServer.func_72939_s(WorldServer.java:489)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:636)
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:334)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:547)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:427)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685)

[LexManos]

When it comes to that, you can't really track it down from a stack trace.

Something is adding/removing a potion effect while they are being itterated over.