21:32:18 [INFO] [ModFixNG] Enabling ModFixNG v1.0
21:32:18 [SEVERE] Error occurred while enabling ModFixNG v1.0 (Is it up to date?)
java.lang.ExceptionInInitializerError
        at modfixng.main.ModFixNG.onEnable(ModFixNG.java:57)
        at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:217)
        at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:467)
        at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:383)
        at org.bukkit.craftbukkit.v1_6_R3.CraftServer.loadPlugin(CraftServer.java:274)
        at org.bukkit.craftbukkit.v1_6_R3.CraftServer.enablePlugins(CraftServer.java:256)
        at cpw.mods.fml.common.event.FMLServerAboutToStartEvent.<init>(FMLServerAboutToStartEvent.java:30)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
        at cpw.mods.fml.common.LoaderState.getEvent(LoaderState.java:84)
        at cpw.mods.fml.common.LoadController.distributeStateMessage(LoadController.java:111)
        at cpw.mods.fml.common.Loader.serverAboutToStart(Loader.java:805)
        at cpw.mods.fml.common.FMLCommonHandler.handleServerAboutToStart(FMLCommonHandler.java:308)
        at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:222)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:626)
        at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)
Caused by: java.lang.RuntimeException: Cannot find class IInventory
        at com.comphenix.protocol.utility.CachedPackage.getPackageClass(CachedPackage.java:78)
        at com.comphenix.protocol.utility.MinecraftReflection.getMinecraftClass(MinecraftReflection.java:1835)
        at modfixng.utils.ModFixNGUtils.<clinit>(ModFixNGUtils.java:61)
        ... 18 more
Caused by: java.lang.ClassNotFoundException: net.minecraft.server.v1_6_R3.IInventory
        at org.bukkit.plugin.java.PluginClassLoader.findClass0(PluginClassLoader.java:442)
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:235)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
        at com.comphenix.protocol.utility.ClassSource$1.loadClass(ClassSource.java:36)
        at com.comphenix.protocol.utility.CachedPackage.getPackageClass(CachedPackage.java:69)
        ... 20 more