SEVERE Comparison method violates its general contract!

FULL PRODUCT VERSION :
java -version
java version "1.7.0_06"
Java(TM) SE Runtime Environment (build 1.7.0_06-b24)
Java HotSpot(TM) 64-Bit Server VM (build 23.2-b09, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Linux user 2.6.32-5-amd64 #1 SMP Sun May 6 04:00:17 UTC 2012 x86_64 GNU/Linux


A DESCRIPTION OF THE PROBLEM :
SEVERE Comparison method violates its general contract!
java.lang.IllegalArgumentException: Comparison method violates its general contract!
at java.util.TimSort.mergeHi(Unknown Source)
at java.util.TimSort.mergeAt(Unknown Source)
at java.util.TimSort.mergeCollapse(Unknown Source)
at java.util.TimSort.sort(Unknown Source)
at java.util.TimSort.sort(Unknown Source)
at java.util.Arrays.sort(Unknown Source)
at net.l2emuproject.gameserver.network.serverpackets.EffectInfoPacket$EffectInfoPacketList.<init>(EffectInfoPacket.java:66)
at net.l2emuproject.gameserver.model.actor.instance.L2PcInstance.updateEffectIcons(L2PcInstance.java:3813)
at net.l2emuproject.gameserver.model.actor.effects.CharEffectList.removeEffect(CharEffectList.java:358)
at net.l2emuproject.gameserver.model.L2Effect.stopEffectTask(L2Effect.java:417)
at net.l2emuproject.gameserver.model.L2Effect.scheduleEffect(L2Effect.java:490)
at net.l2emuproject.gameserver.model.L2Effect$EffectTask.run(L2Effect.java:104)
at net.l2emuproject.util.concurrent.ExecuteWrapper.execute(ExecuteWrapper.java:59)
at net.l2emuproject.util.concurrent.ExecuteWrapper.run(ExecuteWrapper.java:40)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(Unknown Source)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)


REGRESSION. Last worked in version 7


REPRODUCIBILITY :
This bug can be reproduced always.