java.lang.IllegalArgumentException: Failed to register dimension for id 34, One is already registered
at net.minecraftforge.common.DimensionManager.registerDimension(DimensionManager.java:118)
at com.mcjty.rftools.dimension.RfToolsDimensionManager.registerDimensionToServerAndClient(RfToolsDimensionManager.java:174)
at com.mcjty.rftools.dimension.RfToolsDimensionManager.registerDimensions(RfToolsDimensionManager.java:168)
at com.mcjty.rftools.dimension.ModDimensions.initDimensions(ModDimensions.java:18)
at com.mcjty.rftools.RFTools.serverStarted(RFTools.java:180)
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 cpw.mods.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:513)
at sun.reflect.GeneratedMethodAccessor3.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at cpw.mods.fml.common.LoadController.sendEventToModContainer(LoadController.java:208)
at cpw.mods.fml.common.LoadController.propogateStateMessage(LoadController.java:187)
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.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at cpw.mods.fml.common.LoadController.distributeStateMessage(LoadController.java:118)
at cpw.mods.fml.common.Loader.serverStarted(Loader.java:752)
at cpw.mods.fml.common.FMLCommonHandler.handleServerStarted(FMLCommonHandler.java:283)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:389)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685)

The problem in infinity was with Runic Dungeons. It has a problem specifically with dimension 34. Perhaps you should look at that if you have that in your modpack?

Yes that was the problem tnx!!!

More information please? What version of RFTools? Single player/server? When does this happen?

Ah I recognize that problem. That is in infinity right? There was a bug in one version of infinity with another dimension mod that accidentally registered this dimension. Update infinity. It should be fixed now.

It isn't on infinity just my own modpack (mods that i like) the rf version is rftools-2.72, i tried others versions and it still crushes, when i load the world (void world rftools) it crushes, single player world.
Now i have to wait for you to make an update, hopefully it will fix it if not i may have to start another world. Tnx