An error occured while...

org.bukkit.command.CommandException: Unhandled exception executing command 'npc' in plugin Citizens v1.06
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:37)
	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:85)
	at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:255)
	at net.minecraft.server.NetServerHandler.handleCommand(NetServerHandler.java:675)
	at net.minecraft.server.NetServerHandler.chat(NetServerHandler.java:638)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:632)
	at net.minecraft.server.Packet3Chat.a(Packet3Chat.java:32)
	at net.minecraft.server.NetworkManager.a(NetworkManager.java:195)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:74)
	at net.minecraft.server.NetworkListenThread.a(SourceFile:100)
	at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:370)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:285)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:394)
Caused by: java.lang.NoSuchFieldError: a
	at com.fullwall.resources.redecouverte.NPClib.CraftNPC.<init>(CraftNPC.java:28)
	at com.fullwall.resources.redecouverte.NPClib.NPCSpawner.SpawnBasicHumanNpc(NPCSpawner.java:69)
	at com.fullwall.Citizens.BasicNPCHandler.spawnNPC(BasicNPCHandler.java:70)
	at com.fullwall.Citizens.Citizens.createNPC(Citizens.java:392)
	at com.fullwall.Citizens.Citizens.onCommand(Citizens.java:147)
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:35)
	... 12 more