Apparently, putting redstone dust in the bottom of an iron furnace crashes Minecraft, thus corrupting the world because the redstone dust stays in the furnace when the chunks get saved. I haven't tried this yet in 1.70 because I had no idea it had come out yet (yippee) and I'm not sure if putting it in the bottom of a regular furnace does it, either. I'm afraid I can't run the errortest program to get the exact error though, and I'm not even sure IC2 is at the core of the problem (I have a ton of other mods, and I specifically suspect Equivalent Exchange might be to blame if IC2 isn't).
