MobCatcher Error

2013-01-21 23:15:56 [WARNING] [MobCatcher] Task #51447 for MobCatcher v3.3 generated an exception
java.lang.NoClassDefFoundError: org/bukkit/craftbukkit/v1_4_R1/inventory/CraftItemStack
	at me.jordan.mobcatcher.MCSpawnMob.getEggID(MCSpawnMob.java:226)
	at me.jordan.mobcatcher.MCSpawnMob.<init>(MCSpawnMob.java:46)
	at me.jordan.mobcatcher.MCScheduler.spawnThrownEntity(MCScheduler.java:66)
	at me.jordan.mobcatcher.MCScheduler$1.run(MCScheduler.java:40)
	at org.bukkit.craftbukkit.v1_4_6.scheduler.CraftTask.run(CraftTask.java:53)
	at org.bukkit.craftbukkit.v1_4_6.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:345)
	at net.minecraft.server.v1_4_6.MinecraftServer.r(MinecraftServer.java:530)
	at net.minecraft.server.v1_4_6.DedicatedServer.r(DedicatedServer.java:224)
	at net.minecraft.server.v1_4_6.MinecraftServer.q(MinecraftServer.java:494)
	at net.minecraft.server.v1_4_6.MinecraftServer.run(MinecraftServer.java:427)
	at net.minecraft.server.v1_4_6.ThreadServerApplication.run(SourceFile:849)
Caused by: java.lang.ClassNotFoundException: org.bukkit.craftbukkit.v1_4_R1.inventory.CraftItemStack
	at org.bukkit.plugin.java.PluginClassLoader.findClass0(PluginClassLoader.java:70)
	at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:53)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
	... 11 more