WORLDEDIT-2695 - Reported by BSKCraft

This happens after a restart and the first person joins.

9:05:47 AM [SEVERE] java.lang.UnsupportedClassVersionError: MCPCPlusXNmsBlock_147 : Unsupported major.minor version 51.0
9:05:47 AM [SEVERE] at java.lang.ClassLoader.defineClass1(Native Method)
9:05:47 AM [SEVERE] at java.lang.ClassLoader.defineClassCond(Unknown Source)
9:05:47 AM [SEVERE] at java.lang.ClassLoader.defineClass(Unknown Source)
9:05:47 AM [SEVERE] at java.lang.ClassLoader.defineClass(Unknown Source)
9:05:47 AM [SEVERE] at com.sk89q.worldedit.bukkit.BukkitWorld$NmsBlockClassLoader.loadClass(BukkitWorld.java:228)
9:05:47 AM [SEVERE] at com.sk89q.worldedit.bukkit.BukkitWorld.(BukkitWorld.java:146)
9:05:47 AM [SEVERE] at com.sk89q.worldedit.bukkit.BukkitUtil.getLocalWorld(BukkitUtil.java:50)
9:05:47 AM [SEVERE] at com.sk89q.worldedit.bukkit.BukkitPlayer.getWorld(BukkitPlayer.java:132)
9:05:47 AM [SEVERE] at com.sk89q.worldedit.bukkit.WorldEditListener.onPlayerInteract(WorldEditListener.java:121)
9:05:47 AM [SEVERE] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
9:05:47 AM [SEVERE] at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
9:05:47 AM [SEVERE] at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
9:05:47 AM [SEVERE] at java.lang.reflect.Method.invoke(Unknown Source)
9:05:47 AM [SEVERE] at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:425)
9:05:47 AM [SEVERE] at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
9:05:47 AM [SEVERE] at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
9:05:47 AM [SEVERE] at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
9:05:47 AM [SEVERE] at org.bukkit.craftbukkit.v1_4_R1.event.CraftEventFactory.callPlayerInteractEvent(CraftEventFactory.java:178)
9:05:47 AM [SEVERE] at net.minecraft.server.v1_4_R1.PlayerInteractManager.dig(PlayerInteractManager.java:114)
9:05:47 AM [SEVERE] at net.minecraft.server.v1_4_R1.PlayerConnection.a(PlayerConnection.java:564)
9:05:47 AM [SEVERE] at net.minecraft.server.v1_4_R1.Packet14BlockDig.handle(SourceFile:46)
9:05:47 AM [SEVERE] at net.minecraft.server.v1_4_R1.NetworkManager.b(NetworkManager.java:290)
9:05:47 AM [SEVERE] at net.minecraft.server.v1_4_R1.PlayerConnection.d(PlayerConnection.java:113)
9:05:47 AM [SEVERE] at net.minecraft.server.v1_4_R1.ServerConnection.b(SourceFile:39)
9:05:47 AM [SEVERE] at net.minecraft.server.v1_4_R1.DedicatedServerConnection.b(SourceFile:30)
9:05:47 AM [SEVERE] at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:598)
9:05:47 AM [SEVERE] at net.minecraft.server.v1_4_R1.DedicatedServer.r(DedicatedServer.java:224)
9:05:47 AM [SEVERE] at net.minecraft.server.v1_4_R1.MinecraftServer.q(MinecraftServer.java:494)
9:05:47 AM [SEVERE] at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:427)
9:05:47 AM [SEVERE] at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849)
9:05:47 AM [INFO] [WorldEdit] Using inbuilt NmsBlock for this version.