error

2012-01-15 10:34:25 [SEVERE] null
org.bukkit.command.CommandException: Unhandled exception executing command 'gp' in plugin VirtualChest v5.4
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:42)
	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:168)
	at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:385)
	at net.minecraft.server.NetServerHandler.handleCommand(NetServerHandler.java:777)
	at net.minecraft.server.NetServerHandler.chat(NetServerHandler.java:737)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:725)
	at org.getspout.spout.SpoutNetServerHandler.a(SpoutNetServerHandler.java:178)
	at net.minecraft.server.Packet3Chat.handle(Packet3Chat.java:33)
	at net.minecraft.server.NetworkManager.b(NetworkManager.java:226)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:100)
	at org.getspout.spout.SpoutNetServerHandler.a(SpoutNetServerHandler.java:587)
	at net.minecraft.server.NetworkListenThread.a(SourceFile:108)
	at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:536)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:434)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:465)
Caused by: java.lang.NoSuchMethodError: org.bukkit.configuration.MemorySection.isNaturallyStorable(Ljava/lang/Object;)Z
	at com.Balor.Tools.Configuration.ExMemorySection.isNaturallyStorable(ExMemorySection.java:108)
	at com.Balor.Tools.Configuration.File.ExtendedConfiguration.serializeValues(ExtendedConfiguration.java:336)
	at com.Balor.Tools.Configuration.File.ExtendedConfiguration.saveToString(ExtendedConfiguration.java:206)
	at com.Balor.Tools.Configuration.File.ExFileConfiguration.save(ExFileConfiguration.java:66)
	at com.Balor.Tools.Configuration.File.ExtendedConfiguration.save(ExtendedConfiguration.java:124)
	at com.Balor.utils.FilesManager.createDefaultChest(FilesManager.java:445)
	at com.Balor.bukkit.GiftPost.GiftPostWorker.setDefaultChest(GiftPostWorker.java:319)
	at com.Balor.bukkit.GiftPost.GiftPostWorker.getDefaultChest(GiftPostWorker.java:275)
	at com.Balor.commands.Chest.execute(Chest.java:54)
	at com.Balor.bukkit.GiftPost.GiftPost.onCommand(GiftPost.java:285)
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:40)
	... 14 more