(Also, call me a n00b, but I didn't even know you could declare multidimensional arrays fully instantiated like that in Java.)
Hah, I just figured that out a few days ago. My reaction: o_O, followed by embarrassment.
On-topic - I don't see *anywhere* in this class that could throw that exception. And since the arrays are private, it's unlikely outside code is changing them. I hate to even suggest this, but maybe you've hit a bug in the VM? Seems like it's either that, a problem with the class files, or we're all missing something patently obvious.