Pretty repeatable on my world at least.
What I think recreates it is to put a MFSU down on a chunk boundary and cover it with cf foam. Hardened or not it doesn't matter.
when you restart Minecraft it will crash with the following error and the chunk will regenerate wiping out anything that was there before.
java.lang.NullPointerException
at ic2.common.TileEntityCable$1.tickCallback(TileEntityCable.java:153)
at mod_IC2.OnTickInGame(mod_IC2.java:1388)
at ic2.platform.Ic2.onTickInGame(Ic2.java:347)
at ModLoader.onTick(ModLoader.java:1102)
at EntityRendererProxy.b(EntityRendererProxy.java:22)
at net.minecraft.client.Minecraft.x(Minecraft.java:869)
at net.minecraft.client.Minecraft.run(Minecraft.java:747)
at java.lang.Thread.run(Unknown Source)
--- END ERROR REPORT f2357f81 ----------
Tested it with and without the foam. It only crashed when all foamy and stuff.