Running MonsterIRC 1.71, CB-1.3.2-R0.1, HeroChat 5.61 and latest Multiverse-Core dev build I recieved this error in the log:

2012-09-08 14:43:11 [SEVERE] [MonsterIRC - Critical error detected!]
2012-09-08 14:43:11 [SEVERE] java.lang.NullPointerException
2012-09-08 14:43:11 [SEVERE] at org.monstercraft.irc.plugin.managers.listeners.MonsterIRCListener.handleMessage(MonsterIRCListener.java:252)
2012-09-08 14:43:11 [SEVERE] at org.monstercraft.irc.plugin.managers.listeners.MonsterIRCListener.onChat(MonsterIRCListener.java:81)
2012-09-08 14:43:11 [SEVERE] at sun.reflect.GeneratedMethodAccessor280.invoke(Unknown Source)
2012-09-08 14:43:11 [SEVERE] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
2012-09-08 14:43:11 [SEVERE] at java.lang.reflect.Method.invoke(Method.java:601)
2012-09-08 14:43:11 [SEVERE] at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:330)
2012-09-08 14:43:11 [SEVERE] at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
2012-09-08 14:43:11 [SEVERE] at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
2012-09-08 14:43:11 [SEVERE] at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:459)
2012-09-08 14:43:11 [SEVERE] at net.minecraft.server.NetServerHandler.chat(NetServerHandler.java:831)
2012-09-08 14:43:11 [SEVERE] at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:808)
2012-09-08 14:43:11 [SEVERE] at net.minecraft.server.Packet3Chat.handle(Packet3Chat.java:44)
2012-09-08 14:43:11 [SEVERE] at net.minecraft.server.NetworkManager.i(NetworkManager.java:211)
2012-09-08 14:43:11 [SEVERE] at net.minecraft.server.NetworkManager.c(NetworkManager.java:326)
2012-09-08 14:43:11 [SEVERE] at net.minecraft.server.NetworkReaderThread.run(SourceFile:93)

We are using a plugin called pwnfilter that filters the chat from adverts, swearing etc, and it cancels the chat, could it be why?

Does this still occur on the latest build? http://dev.monstercraft.org:8080/job/MonsterIRC/214/