Not sure but I think this means you are using events not existing in CB R5?

11:02:40 [INFO] [MonsterIRC] Identifying with Nickserv....
11:02:40 [SEVERE] Exception in thread "Thread-13"
11:02:40 [SEVERE] java.lang.NoSuchMethodError: org.bukkit.event.Event.(Ljava/lang/String;)V
11:02:40 [SEVERE] at org.monstercraft.irc.plugin.event.IRCEvent.(IRCEvent.java:10)
11:02:40 [SEVERE] at org.monstercraft.irc.plugin.event.events.IRCConnectEvent.(IRCConnectEvent.java:18)
11:02:40 [SEVERE] at org.monstercraft.irc.plugin.managers.handlers.IRCHandler.connect(IRCHandler.java:162)
11:02:40 [SEVERE] at org.monstercraft.irc.MonsterIRC.run(MonsterIRC.java:186)
11:02:40 [SEVERE] at java.lang.Thread.run(Thread.java:722)

irc

done