error

2013-11-30 22:14:25 [WARNING] [SimpleRegionMarket] CHECK.WARN.NO_WORLDNeHoTown
2013-11-30 22:14:25 [SEVERE] Error occurred while enabling SimpleRegionMarket v3.5 (Is it up to date?)
java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
	at java.util.HashMap$KeyIterator.next(Unknown Source)
	at me.ienze.SimpleRegionMarket.TokenManager.checkRegions(TokenManager.java:230)
	at me.ienze.SimpleRegionMarket.SimpleRegionMarket.onEnable(SimpleRegionMarket.java:102)
	at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:217)
	at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:457)
	at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:381)
	at org.bukkit.craftbukkit.v1_6_R3.CraftServer.loadPlugin(CraftServer.java:284)
	at org.bukkit.craftbukkit.v1_6_R3.CraftServer.enablePlugins(CraftServer.java:266)
	at net.minecraft.server.v1_6_R3.MinecraftServer.l(MinecraftServer.java:315)
	at net.minecraft.server.v1_6_R3.MinecraftServer.f(MinecraftServer.java:292)
	at net.minecraft.server.v1_6_R3.MinecraftServer.a(MinecraftServer.java:252)
	at net.minecraft.server.v1_6_R3.DedicatedServer.init(DedicatedServer.java:152)
	at net.minecraft.server.v1_6_R3.MinecraftServer.run(MinecraftServer.java:393)
	at net.minecraft.server.v1_6_R3.ThreadServerApplication.run(SourceFile:583)