Mob Areana Not Working

When using /ma help, I got a message telling me to copy a part of my log here. Can anyone help?

Code:

2012-04-04 17:32:58 [SEVERE] Error occurred while enabling MobArena v0.94.3.24 (Is it up to date?)
java.lang.NoClassDefFoundError: org/bukkit/util/config/Configuration
    at com.garbagemule.MobArena.MobArena.loadConfig(MobArena.java:102)
    at com.garbagemule.MobArena.MobArena.onEnable(MobArena.java:62)
    at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:215)
    at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:336)
    at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:381)
    at org.bukkit.craftbukkit.CraftServer.loadPlugin(CraftServer.java:250)
    at org.bukkit.craftbukkit.CraftServer.enablePlugins(CraftServer.java:232)
    at net.minecraft.server.MinecraftServer.t(MinecraftServer.java:374)
    at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:361)
    at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:187)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:425)
    at net.minecraft.server.ThreadServerApplication.run(SourceFile:490)
Caused by: java.lang.ClassNotFoundException: org.bukkit.util.config.Configuration
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:41)
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:29)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    ... 12 more

 

MobArena is most likely, outdated. Therefore it will not work until it gets updated.