EDIT: I disabled the 'hidden block' in railcraft and it fixed all of the problems, apparently it causes problems with a lot of other mods too.
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The Code door causes me to crash when I have Railcraft installed.
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Description: Unexpected error
java.lang.ClassCastException: mods.railcraft.common.blocks.hidden.TileHidden cannot be cast to mods.immibis.ars.DeFence.TileEntityCodeDoor
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at mods.immibis.ars.DeFence.BlockDFDoor.func_149668_a(BlockDFDoor.java:242)
at net.minecraft.world.World.func_147472_a(World.java:3317)
at mods.immibis.ars.DeFence.ItemCodeDoor.func_77648_a(ItemCodeDoor.java:84)
at net.minecraft.item.ItemStack.func_77943_a(ItemStack.java:129)
at net.minecraft.client.multiplayer.PlayerControllerMP.func_78760_a(PlayerControllerMP.java:360)
at net.minecraft.client.Minecraft.func_147121_ag(Minecraft.java:1435)
at net.minecraft.client.Minecraft.func_71407_l(Minecraft.java:1941)
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:961)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:887)
at net.minecraft.client.main.Main.main(SourceFile:148 )
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28 )