Support request: Unexpected exception cooling a reactor

Hi folks,

Playing around with reactors today. I set up a 1+4 reactor, put in 4 heat spreaders, a stupid amount of uranium and had a ring of ice around the uranium. I set up a redpower system to keep filling it with ice.

I watched it run for a little while, getting a stead 620EU/t according to the meter. I noticed the 4 heat spreaders were getting awfully hot. I then went to have a look at my terraformer to see if it was any faster with the extra power and when I got back to the reactor, I noticed the server had abended with the following error.

[SEVERE] Unexpected exception
java.lang.NullPointerException
	at jb.a(SourceFile:181)
	at ic2.common.TileEntityNuclearReactor.giveHeatTo(TileEntityNuclearReactor.java:706)
	at ic2.common.TileEntityNuclearReactor.generateEnergy(TileEntityNuclearReactor.java:602)
	at ic2.common.TileEntityNuclearReactor.processChamber(TileEntityNuclearReactor.java:488)
	at ic2.common.TileEntityNuclearReactor.processChambers(TileEntityNuclearReactor.java:419)
	at ic2.common.TileEntityNuclearReactor.l_(TileEntityNuclearReactor.java:131)
	at fi.f(World.java:1204)
	at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:446)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:353)
	at cu.run(SourceFile:457)

I have a handful of other plugins loaded. Let me know if you'd like more information.

edit: I can close the server down and it saves its state and exits gracefully. However when I fire it back up, I get the same exception again. Looks like this world file is borked
edit2: Just copied the world folder into Saves and ran it single player. It opens the file, displays the "dirt" background then says Saving Chunks and eventually goes black screen.

Thanks Imer!