skyland error

2013-02-20 18:34:31 [SEVERE] Could not load 'plugins/SkylandsPlus.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.NoClassDefFoundError: com/comphenix/protocol/events/PacketListener
	at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:184)
	at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:305)
	at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:230)
	at org.bukkit.craftbukkit.v1_4_R1.CraftServer.loadPlugins(CraftServer.java:239)
	at org.bukkit.craftbukkit.v1_4_R1.CraftServer.<init>(CraftServer.java:217)
	at net.minecraft.server.v1_4_R1.PlayerList.<init>(PlayerList.java:55)
	at net.minecraft.server.v1_4_R1.DedicatedPlayerList.<init>(SourceFile:11)
	at net.minecraft.server.v1_4_R1.DedicatedServer.init(DedicatedServer.java:104)
	at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:399)
	at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849)
Caused by: java.lang.NoClassDefFoundError: com/comphenix/protocol/events/PacketListener
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:264)
	at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:173)
	... 9 more