Random crash on joining server

[SXScarecrow]

Hi guys, I'm wondering if one of you people can help me out with a perplexing crash....

My modpack, Yogpack Extreme, played fine on a previous server. Then, that server is closed off in favour of a new one. I transfer the exact same files over to it, and do not change my modpack in any way, but now I get this crash upon connecting:

at codechicken.core.ClientUtils.getServerIP(ClientUtils.java:87)

    at codechicken.core.ClientUtils.isLocal(ClientUtils.java:101)

    at codechicken.nei.ClientPacketHandler.handleSMPCheck(ClientPacketHandler.java:107)

    at codechicken.nei.ClientPacketHandler.handlePacket(ClientPacketHandler.java:26)

    at codechicken.core.PacketCustom$ClientPacketHandler.handle(PacketCustom.java:105)

    at codechicken.core.PacketCustom$CustomPacketHandler.onPacketData(PacketCustom.java:74)

    at cpw.mods.fml.common.network.NetworkRegistry.handlePacket(NetworkRegistry.java:243)

    at cpw.mods.fml.common.network.NetworkRegistry.handleCustomPacket(NetworkRegistry.java:233)

    at cpw.mods.fml.common.network.FMLNetworkHandler.handlePacket250Packet(FMLNetworkHandler.java:71)

    at ayh.a(NetClientHandler.java:1483)

    at di.a(SourceFile:59)

    at com.mumfrey.liteloader.core.HookPluginChannels.a(HookPluginChannels.java:99)

    at cg.b(TcpConnection.java:458)

    at cpw.mods.fml.client.FMLClientHandler.disconnectIDMismatch(FMLClientHandler.java:527)

    at cpw.mods.fml.common.FMLCommonHandler.disconnectIDMismatch(FMLCommonHandler.java:464)

    at cpw.mods.fml.common.network.ModIdMapPacket.execute(ModIdMapPacket.java:89)

    at cpw.mods.fml.common.network.FMLNetworkHandler.handleFMLPacket(FMLNetworkHandler.java:102)

    at cpw.mods.fml.common.network.FMLNetworkHandler.handlePacket250Packet(FMLNetworkHandler.java:67)

    at ayh.a(NetClientHandler.java:1483)

    at di.a(SourceFile:59)

    at com.mumfrey.liteloader.core.HookPluginChannels.a(HookPluginChannels.java:99)

    at cg.b(TcpConnection.java:458)

    at ayh.d(NetClientHandler.java:240)

    at ayk.c(GuiConnecting.java:49)

    at net.minecraft.client.Minecraft.l(Minecraft.java:1539)

    at net.minecraft.client.Minecraft.J(Minecraft.java:848)

    at net.minecraft.client.Minecraft.run(Minecraft.java:773)

    at java.lang.Thread.run(Unknown Source)

To say I'm confused is an understatement. Can someone tell me what's up?

[Al3xthegre4t]

I can't help solve it but it looks like the codechickencore core mod can't find the server version of codechickencore, are you sure you might accidentally deleted it out of your servers coremods