S86 Powers Error

2013-04-13 13:15:22 [SEVERE] Error occurred while enabling S86 Powers v4.2.1 (Is it up to date?)
java.lang.NoClassDefFoundError: net/minecraft/server/v1_5_R2/EntitySmallFireball
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(Unknown Source)
	at java.lang.ClassLoader.defineClass(Unknown Source)
	at me.sirrus86.s86powers.powers.services.PowerClassLoader.loadClass(PowerClassLoader.java:42)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at me.sirrus86.s86powers.powers.services.PowersLoader.load(PowersLoader.java:149)
	at me.sirrus86.s86powers.powers.services.PowersLoader.load(PowersLoader.java:109)
	at me.sirrus86.s86powers.powers.services.PowersLoader.load(PowersLoader.java:81)
	at me.sirrus86.s86powers.powers.services.PowersLoader.list(PowersLoader.java:50)
	at me.sirrus86.s86powers.powers.services.PowersLoader.list(PowersLoader.java:32)
	at me.sirrus86.s86powers.powers.PowersHandler.<init>(PowersHandler.java:27)
	at me.sirrus86.s86powers.S86Powers.loadClasses(S86Powers.java:97)
	at me.sirrus86.s86powers.S86Powers.onEnable(S86Powers.java:75)
	at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:217)
	at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:375)
	at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:383)
	at org.bukkit.craftbukkit.v1_5_R2.CraftServer.loadPlugin(CraftServer.java:308)
	at org.bukkit.craftbukkit.v1_5_R2.CraftServer.enablePlugins(CraftServer.java:290)
	at net.minecraft.server.MinecraftServer.j(MinecraftServer.java:314)
	at net.minecraft.server.MinecraftServer.e(MinecraftServer.java:293)
	at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:253)
	at net.minecraft.server.DedicatedServer.init(DedicatedServer.java:154)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:392)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:573)