SSP Server Delogging Me?

[19:29:59] [Server thread/ERROR] [FML]: There was a critical exception handling a packet on channel TerraFirmaCraft
java.lang.NoSuchMethodError: java.util.BitSet.toByteArray()[B
	at com.bioxx.tfc.TileEntities.TEDetailed.isBlockEmpty(TEDetailed.java:67) ~[TEDetailed.class:?]
	at com.bioxx.tfc.Blocks.BlockDetailed.deleteBox(BlockDetailed.java:252) ~[BlockDetailed.class:?]
	at com.bioxx.tfc.Blocks.BlockDetailed.onBlockActivatedServer(BlockDetailed.java:241) ~[BlockDetailed.class:?]
	at com.bioxx.tfc.TileEntities.TEDetailed.handleDataPacket(TEDetailed.java:142) ~[TEDetailed.class:?]
	at com.bioxx.tfc.Handlers.Network.DataBlockPacket.handleServerSide(DataBlockPacket.java:81) ~[DataBlockPacket.class:?]
	at com.bioxx.tfc.Handlers.Network.PacketPipeline.decode(PacketPipeline.java:124) ~[PacketPipeline.class:?]
	at com.bioxx.tfc.Handlers.Network.PacketPipeline.decode(PacketPipeline.java:37) ~[PacketPipeline.class:?]
	at io.netty.handler.codec.MessageToMessageCodec$2.decode(MessageToMessageCodec.java:81) ~[MessageToMessageCodec$2.class:?]
	at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:89) ~[MessageToMessageDecoder.class:?]
	at io.netty.handler.codec.MessageToMessageCodec.channelRead(MessageToMessageCodec.java:111) ~[MessageToMessageCodec.class:?]
	at io.netty.channel.DefaultChannelHandlerContext.invokeChannelRead(DefaultChannelHandlerContext.java:337) ~[DefaultChannelHandlerContext.class:?]
	at io.netty.channel.DefaultChannelHandlerContext.fireChannelRead(DefaultChannelHandlerContext.java:323) ~[DefaultChannelHandlerContext.class:?]
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:785) ~[DefaultChannelPipeline.class:?]
	at io.netty.channel.embedded.EmbeddedChannel.writeInbound(EmbeddedChannel.java:169) ~[EmbeddedChannel.class:?]
	at cpw.mods.fml.common.network.internal.FMLProxyPacket.func_148833_a(FMLProxyPacket.java:77) [FMLProxyPacket.class:?]
	at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:212) [ej.class:?]
	at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:165) [nc.class:?]
	at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:659) [MinecraftServer.class:?]
	at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:547) [MinecraftServer.class:?]
	at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:111) [bsx.class:?]
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:427) [MinecraftServer.class:?]
	at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685) [?:?]
[19:29:59] [Server thread/INFO]: Stopping server
[19:29:59] [Server thread/INFO]: Saving players
[19:29:59] [Server thread/INFO]: Saving worlds
[19:29:59] [Server thread/INFO]: Saving chunks for level 'New World'/DEFAULT
[19:29:59] [Server thread/INFO]: Saving chunks for level 'New World'/Nether
[19:29:59] [Server thread/INFO]: Saving chunks for level 'New World'/DEFAULT
[19:30:00] [Server thread/INFO] [FML]: Unloading dimension 0
[19:30:00] [Server thread/INFO] [FML]: Unloading dimension -1
[19:30:00] [Server thread/INFO] [FML]: Unloading dimension 1
[19:30:00] [Server thread/INFO] [FML]: Applying holder lookups
[19:30:00] [Server thread/INFO] [FML]: Holder lookups applied