Haven't gotten this error till recently. Any help?

12:58:32 [SEVERE] java.lang.NullPointerException
12:58:32 [SEVERE] at com.fullwall.resources.redecouverte.NPClib.NPCSpawner
.RemoveBasicHumanNpc(NPCSpawner.java:101)
12:58:32 [SEVERE] at com.fullwall.Citizens.BasicNPCHandler.despawnNPC(Basi
cNPCHandler.java:436)
12:58:32 [SEVERE] at com.fullwall.Citizens.WorldListen.onChunkUnloaded(Wor
ldListen.java:32)
12:58:32 [SEVERE] at org.bukkit.plugin.java.JavaPluginLoader$35.execute(Ja
vaPluginLoader.java:339)
12:58:32 [SEVERE] at org.bukkit.plugin.RegisteredListener.callEvent(Regist
eredListener.java:59)
12:58:32 [SEVERE] at org.bukkit.plugin.SimplePluginManager.callEvent(Simpl
ePluginManager.java:255)
12:58:32 [SEVERE] at net.minecraft.server.ChunkProviderServer.a(ChunkProvi
derServer.java:216)
12:58:32 [SEVERE] at net.minecraft.server.World.g(World.java:1416)
12:58:32 [SEVERE] at net.minecraft.server.MinecraftServer.h(MinecraftServe
r.java:348)
12:58:32 [SEVERE] at net.minecraft.server.MinecraftServer.run(MinecraftSer
ver.java:272)
12:58:32 [SEVERE] at net.minecraft.server.ThreadServerApplication.run(Sour
ceFile:366)
12:59:58 [INFO] º9[PLAYER_COMMAND] relik0fages: /i sandstone 100
13:01:16 [INFO] [Hawox uQuest] Saving all players quests to file...
13:01:16 [INFO] [Hawox uQuest] Done saving.
13:01:57 [INFO] relik0fages lost connection: disconnect.quitting


________________________________________________________________
Current Server Config:
Bukkit 502
Minecraft 1.3_01

Plugins:
Achievements, AnjoSecurity, Citizens, ClothColor, CommandSigns, CookieMonster, CraftBook, Essentials(all of em), GroupManager,HeroBounty,HiddenDoor,iConomy,iConomyChestShop,Jail,Lampstone,Lockette,LWC,MagicCarpet,mcMMO,MusicCraft,Persistence,SafeKaboom,SignReadMore, Skypirates,Stargate(SW)Stats,Towny,uQuest,WorldEdit,XSigns. (all of them are up-to-date)

 

looks like Citizens to me .. remove it ... test .. redownload .. test ..work ? no? remove config .. test ...