GuestGuard Error

2012-07-10 17:25:37 [SEVERE] Error occurred while enabling GuestGuard v0.6 (Is it up to date?)
org.bukkit.plugin.IllegalPluginAccessException: Unable to find handler list for event org.bukkit.event.player.PlayerEvent
	at org.bukkit.plugin.SimplePluginManager.getRegistrationClass(SimplePluginManager.java:569)
	at org.bukkit.plugin.SimplePluginManager.getRegistrationClass(SimplePluginManager.java:567)
	at org.bukkit.plugin.SimplePluginManager.registerEvents(SimplePluginManager.java:513)
	at us.lupusbukkit.GuestGuard.GuestGuard.onEnable(GuestGuard.java:30)
	at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:215)
	at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:337)
	at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:386)
	at org.bukkit.craftbukkit.CraftServer.loadPlugin(CraftServer.java:264)
	at org.bukkit.craftbukkit.CraftServer.enablePlugins(CraftServer.java:246)
	at net.minecraft.server.MinecraftServer.t(MinecraftServer.java:387)
	at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:374)
	at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:208)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:438)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)