[Launcher crashing on me]

The code im getting the error on is on the bottom. What do i do?

---- Minecraft Crash Report ----

Time: 8/28/13 1:25 AM

Description: Exception in server tick loop

java.lang.NoClassDefFoundError: scala/Function1

at java.lang.Class.getDeclaredConstructors0(Native Method)

at java.lang.Class.privateGetDeclaredConstructors(Unknown Source)

at java.lang.Class.getConstructor0(Unknown Source)

at java.lang.Class.newInstance0(Unknown Source)

at java.lang.Class.newInstance(Unknown Source)

at cpw.mods.fml.common.network.NetworkModHandler.tryCreatingPacketHandler(NetworkModHandler.java:192)

at cpw.mods.fml.common.network.NetworkModHandler.configureNetworkMod(NetworkModHandler.java:140)

at cpw.mods.fml.common.network.NetworkModHandler.<init>(NetworkModHandler.java:99)

at cpw.mods.fml.common.network.FMLNetworkHandler.registerNetworkMod(FMLNetworkHandler.java:262)

at cpw.mods.fml.common.FMLModContainer.constructMod(FMLModContainer.java:465)

at sun.reflect.GeneratedMethodAccessor2.invoke(Unknown Source)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)

at java.lang.reflect.Method.invoke(Unknown Source)

at com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:74)

at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:45)

at com.google.common.eventbus.EventBus.dispatch(EventBus.java:314)

at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:296)

at com.google.common.eventbus.EventBus.post(EventBus.java:267)

at cpw.mods.fml.common.LoadController.sendEventToModContainer(LoadController.java:192)

at cpw.mods.fml.common.LoadController.propogateStateMessage(LoadController.java:172)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)

at java.lang.reflect.Method.invoke(Unknown Source)

at com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:74)

at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:45)

at com.google.common.eventbus.EventBus.dispatch(EventBus.java:314)

at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:296)

at com.google.common.eventbus.EventBus.post(EventBus.java:267)

at cpw.mods.fml.common.LoadController.distributeStateMessage(LoadController.java:103)

at cpw.mods.fml.common.Loader.loadMods(Loader.java:504)

at cpw.mods.fml.server.FMLServerHandler.beginServerLoading(FMLServerHandler.java:85)

at cpw.mods.fml.common.FMLCommonHandler.onServerStart(FMLCommonHandler.java:350)

at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:69)

at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:431)

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

Caused by: java.lang.ClassNotFoundException: scala.Function1

at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:238)

at java.lang.ClassLoader.loadClass(Unknown Source)

at java.lang.ClassLoader.loadClass(Unknown Source)

... 36 more

Caused by: java.lang.NullPointerException

at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:227)

... 38 more