Crash when loading nether with custom block

java.lang.NoClassDefFoundError: net/minecraft/world/CallableLvl1

at net.minecraft.world.World.func_72821_m(World.java:856)

at net.minecraft.world.World.func_72898_h(World.java:781)

at net.minecraft.world.World.func_72851_f(World.java:735)

at net.minecraft.world.World.func_72832_d(World.java:567)

at moreliquids.core.BlockGlowFlowing.updateFlow(BlockGlowFlowing.java:40)

at moreliquids.core.BlockGlowFlowing.func_71847_b(BlockGlowFlowing.java:79)

at net.minecraft.world.WorldServer.func_82740_a(WorldServer.java:480)

at net.minecraft.world.WorldServer.func_72836_a(WorldServer.java:459)

at moreliquids.core.BlockGlowFlowing.func_71861_g(BlockGlowFlowing.java:242)

at net.minecraft.world.chunk.Chunk.func_76592_a(Chunk.java:762)

at net.minecraft.world.World.func_72832_d(World.java:553)

at moreliquids.core.BlockGlowFlowing.flowIntoBlock(BlockGlowFlowing.java:120)

at moreliquids.core.BlockGlowFlowing.func_71847_b(BlockGlowFlowing.java:99)

at moreliquids.core.WorldGenGlowwater.func_76484_a(WorldGenGlowwater.java:89)

at moreliquids.core.WorldGeneratorLiquid.generateNether(WorldGeneratorLiquid.java:26)

at moreliquids.core.WorldGeneratorLiquid.generate(WorldGeneratorLiquid.java:16)

at cpw.mods.fml.common.registry.GameRegistry.generateWorld(GameRegistry.java:102)

at net.minecraft.world.gen.ChunkProviderServer.func_73153_a(ChunkProviderServer.java:259)

at net.minecraft.world.chunk.Chunk.func_76624_a(Chunk.java:1249)

at net.minecraft.world.gen.ChunkProviderServer.func_73158_c(ChunkProviderServer.java:153)

at net.minecraft.world.gen.ChunkProviderServer.func_73154_d(ChunkProviderServer.java:166)

at net.minecraft.world.World.func_72964_e(World.java:522)

at net.minecraft.world.World.func_72798_a(World.java:407)

at net.minecraft.world.Teleporter.func_77184_b(SourceFile:84)

at net.minecraft.world.Teleporter.func_77185_a(SourceFile:49)

at net.minecraft.server.management.ServerConfigurationManager.transferEntityToWorld(ServerConfigurationManager.java:557)

at net.minecraft.server.management.ServerConfigurationManager.transferPlayerToDimension(ServerConfigurationManager.java:482)

at net.minecraft.server.management.ServerConfigurationManager.func_72356_a(ServerConfigurationManager.java:470)

at net.minecraft.entity.player.EntityPlayerMP.func_71027_c(EntityPlayerMP.java:487)

at net.minecraft.entity.Entity.func_70030_z(Entity.java:503)

at net.minecraft.entity.EntityLiving.func_70030_z(EntityLiving.java:582)

at net.minecraft.entity.Entity.func_70071_h_(Entity.java:455)

at net.minecraft.entity.EntityLiving.func_70071_h_(EntityLiving.java:821)

at net.minecraft.entity.player.EntityPlayer.func_70071_h_(EntityPlayer.java:338)

at net.minecraft.entity.player.EntityPlayerMP.func_71127_g(EntityPlayerMP.java:319)

at net.minecraft.network.NetServerHandler.func_72498_a(NetServerHandler.java:308)

at net.minecraft.network.packet.Packet10Flying.func_73279_a(SourceFile:136)

at net.minecraft.network.MemoryConnection.func_74428_b(MemoryConnection.java:89)

at net.minecraft.network.NetServerHandler.func_72570_d(NetServerHandler.java:134)

at net.minecraft.network.NetworkListenThread.func_71747_b(NetworkListenThread.java:53)

at net.minecraft.server.integrated.IntegratedServerListenThread.func_71747_b(IntegratedServerListenThread.java:109)

at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:674)

at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:570)

at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:127)

at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:468)

at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:573)

package moreliquids.core;

import java.util.Random;

import net.minecraft.world.World;

import net.minecraft.world.chunk.IChunkProvider;

import cpw.mods.fml.common.IWorldGenerator;

import moreliquids.MoreLiquids;

public class WorldGeneratorLiquid implements IWorldGenerator

{

@Override

public void generate(Random random, int chunkX, int chunkZ, World world,IChunkProvider chunkGenerator, IChunkProvider chunkProvider)

{

if(world.provider.isHellWorld)

generateNether(world, random, chunkX*16, chunkZ*16);

}

private void generateNether(World world, Random random, int i, int j)

{

for(int k1 = 0; k1 < 20; k1++)

{

int l2 = i + random.nextInt(16) + 8;

int i4 = random.nextInt(random.nextInt(96) + 16);

int i5 = j + random.nextInt(16) + 8;

(new WorldGenGlowwater(MoreLiquids.glowMoving.blockID, false)).generate(world, random, l2, i4, i5);

}

}

}

package moreliquids.core;

import java.util.Random;

import net.minecraft.block.Block;

import net.minecraft.world.*;

import net.minecraft.world.gen.feature.*;

public class WorldGenGlowwater extends WorldGenerator

{

    private int hellLavaID;

    private boolean field_94524_b = false;

    public WorldGenGlowwater(int par1, boolean par2)

    {

        this.hellLavaID = par1;

        this.field_94524_b = par2;

    }

    public boolean generate(World par1World, Random par2Random, int par3, int par4, int par5)

    {

        if (par1World.getBlockId(par3, par4 + 1, par5) != Block.netherrack.blockID)

        {

            return false;

        }

        else if (par1World.getBlockId(par3, par4, par5) != 0 && par1World.getBlockId(par3, par4, par5) != Block.netherrack.blockID)

        {

            return false;

        }

        else

        {

            int l = 0;

            if (par1World.getBlockId(par3 - 1, par4, par5) == Block.netherrack.blockID)

            {

                ++l;

            }

            if (par1World.getBlockId(par3 + 1, par4, par5) == Block.netherrack.blockID)

            {

                ++l;

            }

            if (par1World.getBlockId(par3, par4, par5 - 1) == Block.netherrack.blockID)

            {

                ++l;

            }

            if (par1World.getBlockId(par3, par4, par5 + 1) == Block.netherrack.blockID)

            {

                ++l;

            }

            if (par1World.getBlockId(par3, par4 - 1, par5) == Block.netherrack.blockID)

            {

                ++l;

            }

            int i1 = 0;

            if (par1World.isAirBlock(par3 - 1, par4, par5))

            {

                ++i1;

            }

            if (par1World.isAirBlock(par3 + 1, par4, par5))

            {

                ++i1;

            }

            if (par1World.isAirBlock(par3, par4, par5 - 1))

            {

                ++i1;

            }

            if (par1World.isAirBlock(par3, par4, par5 + 1))

            {

                ++i1;

            }

            if (par1World.isAirBlock(par3, par4 - 1, par5))

            {

                ++i1;

            }

            if (!this.field_94524_b && l == 4 && i1 == 1 || l == 5)

            {

                par1World.setBlock(par3, par4, par5, this.hellLavaID, 0, 2);

                par1World.scheduledUpdatesAreImmediate = true;

                Block.blocksList[this.hellLavaID].updateTick(par1World, par3, par4, par5, par2Random);

                par1World.scheduledUpdatesAreImmediate = false;

            }

            return true;

        }

    }

}