Bukkit

23:23:38 [WARNING] Could not properly handle event BLOCK_PHYSICS:
java.lang.IllegalAccessError: Synchronized code got accessed from another thread: net.dmg2.RegenBlock.RegenBlockQueue
        at org.bukkit.event.NLTCListener.onBlockPhysics(NLTCListener:0)
        at sun.reflect.GeneratedMethodAccessor49.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:601)
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:339)
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
        at net.minecraft.server.World.m(World.java:432)
        at net.minecraft.server.World.applyPhysics(World.java:417)
        at net.minecraft.server.World.update(World.java:373)
        at net.minecraft.server.World.setTypeId(World.java:345)
        at org.bukkit.craftbukkit.block.CraftBlock.setTypeId(CraftBlock.java:92)
        at net.dmg2.RegenBlock.RegenBlockEventListenerBlock.onEvent(RegenBlockEventListenerBlock.java:65)
        at sun.reflect.GeneratedMethodAccessor32.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:601)
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:339)
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
        at net.dmg2.RegenBlock.RegenBlockQueue.run(RegenBlockQueue.java:101)
23:23:38 [INFO] This error is logged only once: it could have occurred multiple times by now.
23:23:38 [INFO] Potential failures may occur in other plugins handling this Event.
23:23:38 [INFO] Please contact one of the authors of plugin 'RegenBlock':