[18:43:22 WARN]: Exception in thread "Craft Scheduler Thread - 9"
[18:43:22 WARN]: org.apache.commons.lang.UnhandledException: Plugin face_guilds v1.1 generated an exception while executing task 4025
        at org.bukkit.craftbukkit.v1_7_R4.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:56)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)
Caused by: java.util.ConcurrentModificationException
        at java.util.WeakHashMap$HashIterator.nextEntry(WeakHashMap.java:806)
        at java.util.WeakHashMap$ValueIterator.next(WeakHashMap.java:833)
        at net.karolek.revoguild.tablist.update.TabHighUpdateTask.run(TabHighUpdateTask.java:15)
        at org.bukkit.craftbukkit.v1_7_R4.scheduler.CraftTask.run(CraftTask.java:71)
        at org.bukkit.craftbukkit.v1_7_R4.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:53)
        ... 3 more