[10:02:19 WARN]: Exception in thread "Craft Scheduler Thread - 10729"
[10:02:19 WARN]: org.apache.commons.lang.UnhandledException: Plugin PvPTimer v1.3 generated an exception while executing task 1710883
        at org.bukkit.craftbukkit.v1_7_R3.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:56)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:745)
Caused by: java.util.ConcurrentModificationException
        at java.util.HashMap$HashIterator.nextEntry(HashMap.java:922)
        at java.util.HashMap$KeyIterator.next(HashMap.java:956)
        at lemon42.PvPTimer.CheckTask.run(CheckTask.java:13)
        at org.bukkit.craftbukkit.v1_7_R3.scheduler.CraftTask.run(CraftTask.java:67)
        at org.bukkit.craftbukkit.v1_7_R3.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:53)
        ... 3 more