/Help is an unknown command for OPs (Minecraft FTB)

[INFO] [STDERR] java.lang.IllegalArgumentException: Comparison method violates its general contract!
[INFO] [STDERR]     at java.util.ComparableTimSort.mergeLo(Unknown Source)
[INFO] [STDERR]     at java.util.ComparableTimSort.mergeAt(Unknown Source)
[INFO] [STDERR]     at java.util.ComparableTimSort.mergeCollapse(Unknown Source)
[INFO] [STDERR]     at java.util.ComparableTimSort.sort(Unknown Source)
[INFO] [STDERR]     at java.util.ComparableTimSort.sort(Unknown Source)
[INFO] [STDERR]     at java.util.Arrays.sort(Unknown Source)
[INFO] [STDERR]     at java.util.Collections.sort(Unknown Source)
[INFO] [STDERR]     at net.minecraft.command.CommandHelp.func_71534_d(SourceFile:74)
[INFO] [STDERR]     at net.minecraft.command.CommandHelp.func_71515_b(SourceFile:36)
[INFO] [STDERR]     at net.minecraft.command.CommandHandler.func_71556_a(CommandHandler.java:88)
[INFO] [STDERR]     at net.minecraft.server.dedicated.DedicatedServer.func_71333_ah(DedicatedServer.java:315)
[INFO] [STDERR]     at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:277)
[INFO] [STDERR]     at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:587)
[INFO] [STDERR]     at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:484)
[INFO] [STDERR]     at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)