When I import this world using Spigot, I get this error. All other plugins work properly. Yours will occasionally work if I delete the configuration files and the world. This error is also present in older spigot builds running 1.6.2-R0.1 and likely normal craftbukkit as well.

2013-08-14 07:06:26 [INFO] This server is running CraftBukkit version git-Spigot-1080 (MC: 1.6.2) (Implementing API version 1.6.2-R0.2-SNAPSHOT)

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2013-08-14 07:07:09 [INFO] [173generator] 173generator enabled for ember, world seed: 9000526113235493476
2013-08-14 07:07:09 [SEVERE] net.minecraft.server.v1_6_R2.ReportedException: Exception generating new chunk
2013-08-14 07:07:09 [SEVERE] at net.minecraft.server.v1_6_R2.World.(World.java:205)
2013-08-14 07:07:09 [SEVERE] at net.minecraft.server.v1_6_R2.WorldServer.(WorldServer.java:47)
2013-08-14 07:07:09 [SEVERE] at org.bukkit.craftbukkit.v1_6_R2.CraftServer.createWorld(CraftServer.java:724)
2013-08-14 07:07:09 [SEVERE] at org.bukkit.Bukkit.createWorld(Bukkit.java:226)
2013-08-14 07:07:09 [SEVERE] at org.bukkit.WorldCreator.createWorld(WorldCreator.java:235)
2013-08-14 07:07:09 [SEVERE] at com.onarandombox.MultiverseCore.utils.WorldManager.doLoad(WorldManager.java:421)
2013-08-14 07:07:09 [SEVERE] at com.onarandombox.MultiverseCore.utils.WorldManager.addWorld(WorldManager.java:229)
2013-08-14 07:07:09 [SEVERE] at com.onarandombox.MultiverseCore.commands.CreateCommand.runCommand(CreateCommand.java:114)
2013-08-14 07:07:09 [SEVERE] at com.pneumaticraft.commandhandler.multiverse.CommandHandler.checkAndRunCommand(CommandHandler.java:279)
2013-08-14 07:07:09 [SEVERE] at com.pneumaticraft.commandhandler.multiverse.CommandHandler.processFoundCommands(CommandHandler.java:143)
2013-08-14 07:07:09 [SEVERE] at com.pneumaticraft.commandhandler.multiverse.CommandHandler.locateAndRunCommand(CommandHandler.java:93)
2013-08-14 07:07:09 [SEVERE] at com.onarandombox.MultiverseCore.MultiverseCore.onCommand(MultiverseCore.java:894)
2013-08-14 07:07:09 [SEVERE] at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44)
2013-08-14 07:07:09 [SEVERE] at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:192)
2013-08-14 07:07:09 [SEVERE] at org.bukkit.craftbukkit.v1_6_R2.CraftServer.dispatchCommand(CraftServer.java:527)
2013-08-14 07:07:09 [SEVERE] at org.bukkit.craftbukkit.v1_6_R2.CraftServer.dispatchServerCommand(CraftServer.java:516)
2013-08-14 07:07:09 [SEVERE] at net.minecraft.server.v1_6_R2.DedicatedServer.ar(DedicatedServer.java:275)
2013-08-14 07:07:09 [SEVERE] at net.minecraft.server.v1_6_R2.DedicatedServer.t(DedicatedServer.java:240)
2013-08-14 07:07:09 [SEVERE] at net.minecraft.server.v1_6_R2.MinecraftServer.s(MinecraftServer.java:481)
2013-08-14 07:07:09 [SEVERE] at net.minecraft.server.v1_6_R2.MinecraftServer.run(MinecraftServer.java:413)
2013-08-14 07:07:09 [SEVERE] at net.minecraft.server.v1_6_R2.ThreadServerApplication.run(SourceFile:582)
2013-08-14 07:07:09 [SEVERE] Caused by: java.lang.NullPointerException
2013-08-14 07:07:09 [SEVERE] at com.github.barteks2x.b173gen.reflection.WorldGenBaseRef.generate(WorldGenBaseRef.java:32)
2013-08-14 07:07:09 [SEVERE] at com.github.barteks2x.b173gen.generator.ChunkProviderGenerate.generateBlockSections(ChunkProviderGenerate.java:227)
2013-08-14 07:07:09 [SEVERE] at org.bukkit.craftbukkit.v1_6_R2.generator.CustomChunkGenerator.getOrCreateChunk(CustomChunkGenerator.java:98)
2013-08-14 07:07:09 [SEVERE] at net.minecraft.server.v1_6_R2.ChunkProviderServer.getChunkAt(ChunkProviderServer.java:112)
2013-08-14 07:07:09 [SEVERE] at net.minecraft.server.v1_6_R2.ChunkProviderServer.getChunkAt(ChunkProviderServer.java:84)
2013-08-14 07:07:09 [SEVERE] at net.minecraft.server.v1_6_R2.ChunkProviderServer.getOrCreateChunk(ChunkProviderServer.java:160)
2013-08-14 07:07:09 [SEVERE] at net.minecraft.server.v1_6_R2.World.getChunkAt(World.java:329)
2013-08-14 07:07:09 [SEVERE] at net.minecraft.server.v1_6_R2.World.getTypeId(World.java:254)
2013-08-14 07:07:09 [SEVERE] at org.bukkit.craftbukkit.v1_6_R2.CraftWorld.getBlockTypeIdAt(CraftWorld.java:86)
2013-08-14 07:07:09 [SEVERE] at com.github.barteks2x.b173gen.generator.ChunkProviderGenerate.canSpawn(ChunkProviderGenerate.java:740)
2013-08-14 07:07:09 [SEVERE] at com.github.barteks2x.b173gen.generator.ChunkProviderGenerate.getFixedSpawnLocation(ChunkProviderGenerate.java:752)
2013-08-14 07:07:09 [SEVERE] at net.minecraft.server.v1_6_R2.WorldServer.b(WorldServer.java:707)
2013-08-14 07:07:09 [SEVERE] at net.minecraft.server.v1_6_R2.WorldServer.a(WorldServer.java:687)
2013-08-14 07:07:09 [SEVERE] at net.minecraft.server.v1_6_R2.World.(World.java:195)
2013-08-14 07:07:09 [SEVERE] ... 20 more
2013-08-14 07:07:09 [SEVERE] [Multiverse-Core] The world 'ember' could NOT be loaded because it contains errors!
2013-08-14 07:07:09 [SEVERE] [Multiverse-Core] Try using Chukster to repair your world! 'ember'
2013-08-14 07:07:09 [SEVERE] [Multiverse-Core] http://forums.bukkit.org/threads/admin-chunkster.8186/
2013-08-14 07:07:09 [SEVERE] [Multiverse-Core] Failed to Create/Load the world 'ember'

Fixed.