Server Crashing When Generating Nether

Hi, my server has crashed several times now when generating chunks in the nether...I don't really know what the issue is...here is the error message it floods my screen with:

1:36:54 AM [SEVERE] java.lang.reflect.InvocationTargetException
1:36:54 AM [SEVERE] at sun.reflect.GeneratedMethodAccessor80.invoke(Unknown Source)
1:36:54 AM [SEVERE] at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
1:36:54 AM [SEVERE] at java.lang.reflect.Method.invoke(Unknown Source)
1:36:54 AM [SEVERE] at org.getspout.spout.block.mcblock.CustomMCBlock.intercept(CustomMCBlock.java:546)
1:36:54 AM [SEVERE] at net.minecraft.server.v1_6_R3.BlockFlowing$$EnhancerByCGLIB$$25f6c218.a(<generated>)
1:36:54 AM [SEVERE] at net.minecraft.server.v1_6_R3.WorldGenHellLava.a(SourceFile:39)
1:36:54 AM [SEVERE] at net.minecraft.server.v1_6_R3.ChunkProviderHell.getChunkAt(SourceFile:325)
1:36:54 AM [SEVERE] at org.bukkit.craftbukkit.v1_6_R3.generator.NormalChunkGenerator.getChunkAt(NormalChunkGenerator.java:49)
1:36:54 AM [SEVERE] at net.minecraft.server.v1_6_R3.ChunkProviderServer.getChunkAt(ChunkProviderServer.java:225)
1:36:54 AM [SEVERE] at net.minecraft.server.v1_6_R3.Chunk.a(Chunk.java:796)
1:36:54 AM [SEVERE] at org.bukkit.craftbukkit.v1_6_R3.chunkio.ChunkIOProvider.callStage2(ChunkIOProvider.java:61)
1:36:54 AM [SEVERE] at org.bukkit.craftbukkit.v1_6_R3.chunkio.ChunkIOProvider.callStage2(ChunkIOProvider.java:13)
1:36:54 AM [SEVERE] at org.bukkit.craftbukkit.v1_6_R3.util.AsynchronousExecutor$Task.finish(AsynchronousExecutor.java:179)
1:36:54 AM [SEVERE] at org.bukkit.craftbukkit.v1_6_R3.util.AsynchronousExecutor.finishActive(AsynchronousExecutor.java:287)
1:36:54 AM [SEVERE] at org.bukkit.craftbukkit.v1_6_R3.chunkio.ChunkIOExecutor.tick(ChunkIOExecutor.java:30)
1:36:54 AM [SEVERE] at net.minecraft.server.v1_6_R3.MinecraftServer.t(MinecraftServer.java:531)
1:36:54 AM [SEVERE] at net.minecraft.server.v1_6_R3.DedicatedServer.t(DedicatedServer.java:227)
1:36:54 AM [SEVERE] at net.minecraft.server.v1_6_R3.MinecraftServer.s(MinecraftServer.java:488)
1:36:54 AM [SEVERE] at net.minecraft.server.v1_6_R3.MinecraftServer.run(MinecraftServer.java:421)
1:36:54 AM [SEVERE] at net.minecraft.server.v1_6_R3.ThreadServerApplication.run(SourceFile:583)
1:36:54 AM [SEVERE] Caused by: java.lang.reflect.InvocationTargetException
1:36:54 AM [SEVERE] at sun.reflect.GeneratedMethodAccessor79.invoke(Unknown Source)
1:36:54 AM [SEVERE] at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
1:36:54 AM [SEVERE] at java.lang.reflect.Method.invoke(Unknown Source)
1:36:54 AM [SEVERE] at org.getspout.spout.block.mcblock.CustomMCBlock.intercept

 

If it is an already generated world use a utility like this to search for and fix errors : http://www.minecraftforum.net/topic/302380-minecraft-region-fixer/

If it is not, then try getting the latest build of bukkit.