Bukkit

What steps will reproduce the problem?
1. Startup Server
2. Use command "/voyage create" (Or "/voyage createblaze")
3. Wait a few minutes

What is the expected output? What do you see instead?
I've expected to receive a dragon or blaze which could be made to go on set paths. Instead, a few minutes after I use said commands, the server crashes.

What version of the product are you using?
Latest version.

Do you have an error log of what happened?

java.lang.NoSuchMethodError: net.minecraft.server.NBTTagCompound.setBoolean(Ljava/lang/String;Z)V
   at com.thevoxelbox.voyage.PrzlabsDragon.b(PrzlabsDragon.java:338)
   at net.minecraft.server.Entity.d(Entity.java:943)
   at net.minecraft.server.Entity.c(Entity.java:910)
   at net.minecraft.server.ChunkLoader.a(SourceFile:125)
   at net.minecraft.server.ChunkRegionLoader.a(SourceFile:84)
   at net.minecraft.server.ChunkProviderServer.saveChunk(ChunkProviderServer.java:152)
   at net.minecraft.server.ChunkProviderServer.saveChunks(ChunkProviderServer.java:201)
   at net.minecraft.server.World.save(World.java:267)
   at net.minecraft.server.World.doTick(World.java:1733)
   at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:503)
   at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:414)
   at net.minecraft.server.ThreadServerApplication.run(SourceFile:457)
Unexpected exception
java.lang.NoSuchMethodError: net.minecraft.server.NBTTagCompound.setBoolean(Ljava/lang/String;Z)V
   at com.thevoxelbox.voyage.PrzlabsDragon.b(PrzlabsDragon.java:338)
   at net.minecraft.server.Entity.d(Entity.java:943)
   at net.minecraft.server.Entity.c(Entity.java:910)
   at net.minecraft.server.ChunkLoader.a(SourceFile:125)
   at net.minecraft.server.ChunkRegionLoader.a(SourceFile:84)
   at net.minecraft.server.ChunkProviderServer.saveChunk(ChunkProviderServer.java:152)
   at net.minecraft.server.ChunkProviderServer.saveChunks(ChunkProviderServer.java:201)
   at net.minecraft.server.World.save(World.java:267)
   at net.minecraft.server.World.doTick(World.java:1733)
   at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:503)
   at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:414)
   at net.minecraft.server.ThreadServerApplication.run(SourceFile:457)

Please provide any additional information below.

I have tried removing almost all other plugins, with the exception of other voxel plugins, in case those are causing this issue. This has changed nothing, and has left it still giving me this error when used.

Uhhhhhh ... Right.. Maybe you could tell me what Version of Minecraft this is?