Getting this error when I attempt to load a world.

[IIsamonkey]

2013-01-29 20:08:18 [INFO] [STDERR] Exception in thread "Server thread" java.lang.IllegalArgumentException: Failed to register dimension for id 7, One is already registered
2013-01-29 20:08:18 [INFO] [STDERR]    at net.minecraftforge.common.DimensionManager.registerDimension(DimensionManager.java:83)
2013-01-29 20:08:18 [INFO] [STDERR]    at xcompwiz.mystcraft.Mystcraft.registerDimensions(Mystcraft.java:228)
2013-01-29 20:08:18 [INFO] [STDERR]    at xcompwiz.mystcraft.Mystcraft.registerCommands(Mystcraft.java:188)
2013-01-29 20:08:18 [INFO] [STDERR]    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
2013-01-29 20:08:18 [INFO] [STDERR]    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
2013-01-29 20:08:18 [INFO] [STDERR]    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
2013-01-29 20:08:18 [INFO] [STDERR]    at java.lang.reflect.Method.invoke(Unknown Source)
2013-01-29 20:08:18 [INFO] [STDERR]    at cpw.mods.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:487)
2013-01-29 20:08:18 [INFO] [STDERR]    at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
2013-01-29 20:08:18 [INFO] [STDERR]    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
2013-01-29 20:08:18 [INFO] [STDERR]    at java.lang.reflect.Method.invoke(Unknown Source)
2013-01-29 20:08:18 [INFO] [STDERR]    at com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:69)
2013-01-29 20:08:18 [INFO] [STDERR]    at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:45)
2013-01-29 20:08:18 [INFO] [STDERR]    at com.google.common.eventbus.EventBus.dispatch(EventBus.java:317)
2013-01-29 20:08:18 [INFO] [STDERR]    at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:300)
2013-01-29 20:08:18 [INFO] [STDERR]    at com.google.common.eventbus.EventBus.post(EventBus.java:268)
2013-01-29 20:08:18 [INFO] [STDERR]    at cpw.mods.fml.common.LoadController.propogateStateMessage(LoadController.java:140)
2013-01-29 20:08:18 [INFO] [STDERR]    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
2013-01-29 20:08:18 [INFO] [STDERR]    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
2013-01-29 20:08:18 [INFO] [STDERR]    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
2013-01-29 20:08:18 [INFO] [STDERR]    at java.lang.reflect.Method.invoke(Unknown Source)
2013-01-29 20:08:18 [INFO] [STDERR]    at com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:69)
2013-01-29 20:08:18 [INFO] [STDERR]    at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:45)
2013-01-29 20:08:18 [INFO] [STDERR]    at com.google.common.eventbus.EventBus.dispatch(EventBus.java:317)
2013-01-29 20:08:18 [INFO] [STDERR]    at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:300)
2013-01-29 20:08:18 [INFO] [STDERR]    at com.google.common.eventbus.EventBus.post(EventBus.java:268)
2013-01-29 20:08:18 [INFO] [STDERR]    at cpw.mods.fml.common.LoadController.distributeStateMessage(LoadController.java:83)
2013-01-29 20:08:18 [INFO] [STDERR]    at cpw.mods.fml.common.Loader.serverStarting(Loader.java:702)
2013-01-29 20:08:18 [INFO] [STDERR]    at cpw.mods.fml.common.FMLCommonHandler.handleServerStarting(FMLCommonHandler.java:314)
2013-01-29 20:08:18 [INFO] [STDERR]    at bdz.c(IntegratedServer.java:103)
2013-01-29 20:08:18 [INFO] [STDERR]    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:458)
2013-01-29 20:08:18 [INFO] [STDERR]    at fy.run(SourceFile:849)

There is a full version of this here: http://pastebin.com/CMD8TTU0

 

[Nessiroj]

In the configfiles on the server / cleint you need to change the Dimension ID for Twilightforest (in twilightforest.cfg) from 7 to something above 100

 

[Kuraxt]

I was having the exact same error and your solution did it! A thousand thanks!