[Haskell-cafe] Crash!

Well what do you know? I have actually managed to write a pure Haskell program that generates an actual access violation when run! o_O I was under the impression that this is impossible, so I'm now slightly worried. The weird thing is, I spent 4 hours using the program without issue. However, when you feed it one specific input, it crashes. And I'm really not sure why. However, it appears to crash while asking GTK to save a PNG file. (??) That doesn't make a lot of sense, obviously. I do have some calls to unsafe array functions, but that doesn't appear to be where the crash is happening. Does anybody have any clue where I start with trying to diagnose this? I'm out of my depth...