entitysuppressor-error

2012-06-17 18:00:53 [INFO] CONSOLE: Forcing save..
2012-06-17 18:00:54 [INFO] CONSOLE: Save complete.
2012-06-17 18:00:57 [SEVERE] java.util.ConcurrentModificationException
2012-06-17 18:00:57 [SEVERE] 	at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:819)
2012-06-17 18:00:57 [SEVERE] 	at java.util.ArrayList$Itr.next(ArrayList.java:791)
2012-06-17 18:00:57 [SEVERE] 	at org.bukkit.craftbukkit.CraftWorld.getLivingEntities(CraftWorld.java:556)
2012-06-17 18:00:57 [SEVERE] 	at com.fishrock123.entitysuppressor.utils.CustomPlotters$2.getValue(CustomPlotters.java:25)
2012-06-17 18:00:57 [SEVERE] 	at com.fishrock123.entitysuppressor.utils.Metrics.postPlugin(Metrics.java:362)
2012-06-17 18:00:57 [SEVERE] 	at com.fishrock123.entitysuppressor.utils.Metrics.access$4(Metrics.java:325)
2012-06-17 18:00:57 [SEVERE] 	at com.fishrock123.entitysuppressor.utils.Metrics$1.run(Metrics.java:243)
2012-06-17 18:00:57 [SEVERE] 	at org.bukkit.craftbukkit.scheduler.CraftWorker.run(CraftWorker.java:34)
2012-06-17 18:00:57 [SEVERE] 	at java.lang.Thread.run(Thread.java:722)

[...]

2012-06-17 18:10:58 [SEVERE] java.util.ConcurrentModificationException
2012-06-17 18:10:58 [SEVERE] 	at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:819)
2012-06-17 18:10:58 [SEVERE] 	at java.util.ArrayList$Itr.next(ArrayList.java:791)
2012-06-17 18:10:58 [SEVERE] 	at org.bukkit.craftbukkit.CraftWorld.getEntities(CraftWorld.java:538)
2012-06-17 18:10:58 [SEVERE] 	at com.fishrock123.entitysuppressor.utils.CustomPlotters$1.getValue(CustomPlotters.java:14)
2012-06-17 18:10:58 [SEVERE] 	at com.fishrock123.entitysuppressor.utils.Metrics.postPlugin(Metrics.java:362)
2012-06-17 18:10:58 [SEVERE] 	at com.fishrock123.entitysuppressor.utils.Metrics.access$4(Metrics.java:325)
2012-06-17 18:10:58 [SEVERE] 	at com.fishrock123.entitysuppressor.utils.Metrics$1.run(Metrics.java:243)
2012-06-17 18:10:58 [SEVERE] 	at org.bukkit.craftbukkit.scheduler.CraftWorker.run(CraftWorker.java:34)
2012-06-17 18:10:58 [SEVERE] 	at java.lang.Thread.run(Thread.java:722)