Problem Direwolf20 server crash - report included

[Vaupell]

Server crash during the night, and it appears to be something to do with railcraft ?

full report : http://pastebin.com/tNgDfbNy

Part of the report :

java.lang.ClassCastException: akp cannot be cast to railcraft.common.blocks.machine.BlockMachine
        at railcraft.common.blocks.machine.TileMachineBase.g(TileMachineBase.java:137)
        at railcraft.common.blocks.machine.TileMultiBlock.g(TileMultiBlock.java:103)
        at railcraft.common.blocks.machine.beta.TileTankIron.g(TileTankIron.java:213)
        at yc.h(World.java:2155)
        at in.h(WorldServer.java:514)
        at net.minecraft.server.MinecraftServer.r(MinecraftServer.java:679)
        at ho.r(DedicatedServer.java:270)
        at net.minecraft.server.MinecraftServer.q(MinecraftServer.java:598)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:497)
        at fy.run(SourceFile:849)

Suggestions ?