Bukkit

What steps will reproduce the problem?
1. Try to use a lobby sign to join a game
2. Nothing appears in in-game chat
3. Below error is shown in console

What is the expected output? What do you see instead?
[18:34:30 ERROR]: Could not pass event PlayerInteractEvent to Quake v2.0.1
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:427) ~[craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:481) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:466) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        at org.bukkit.craftbukkit.v1_7_R1.event.CraftEventFactory.callPlayerInteractEvent(CraftEventFactory.java:191) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        at net.minecraft.server.v1_7_R1.PlayerInteractManager.interact(PlayerInteractManager.java:374) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        at net.minecraft.server.v1_7_R1.PlayerConnection.a(PlayerConnection.java:628) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        at net.minecraft.server.v1_7_R1.PacketPlayInBlockPlace.a(SourceFile:60) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        at net.minecraft.server.v1_7_R1.PacketPlayInBlockPlace.handle(SourceFile:9) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        at net.minecraft.server.v1_7_R1.NetworkManager.a(NetworkManager.java:146) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        at net.minecraft.server.v1_7_R1.ServerConnection.c(SourceFile:134) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        at net.minecraft.server.v1_7_R1.MinecraftServer.u(MinecraftServer.java:655) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        at net.minecraft.server.v1_7_R1.DedicatedServer.u(DedicatedServer.java:250) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        at net.minecraft.server.v1_7_R1.MinecraftServer.t(MinecraftServer.java:545) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:457) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
Caused by: java.lang.NoClassDefFoundError: org/bukkit/craftbukkit/v1_6_R3/entity/CraftPlayer
        at com.Geekpower14.Quake.Utils.PlayerSerializer.PlayerToConfig(PlayerSerializer.java:29) ~[?:?]
        at com.Geekpower14.Quake.Arena.APlayer.SaveInventory(APlayer.java:99) ~[?:?]
        at com.Geekpower14.Quake.Arena.APlayer.<init>(APlayer.java:61) ~[?:?]
        at com.Geekpower14.Quake.Arena.SArena.joinArena(SArena.java:248) ~[?:?]
        at com.Geekpower14.Quake.Listener.PlayerListener.onPlayerInteract(PlayerListener.java:128) ~[?:?]
        at sun.reflect.GeneratedMethodAccessor111.invoke(Unknown Source) ~[?:?]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.7.0_25]
        at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.7.0_25]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:425) ~[craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
        ... 15 more

What version of the product are you using?
Quake - Beta V2.4.0 but when i use /quake it says I'm running V2.3.0 even though I've made sure its the right version twice.