Simple question: How do I figure out where Y is? It's a memory address (I'm guessing) and not a line number. I'm using VS2010.

Does VS have a window I don't know about that contains the memory addresses of functions currently in use?

Sorry, I can't post code, it's a couple hundred k spread over dozens of files, plus I'd have to hassle with NDAs and crap if I wanted to share it with anyone.

Also, I'm well aware that the code sucks so if that's the only thing you want to reply with, I've saved you the effort. :)

I'm not a memory debugging expert, but you can try to instrument your code with some of the techniques described here. If Y is accessed with a 'dangling' pointer you have good chances of finding the problem. Sometimes you can also guess from what was written, from where it was written. Here the Memory Window is useful.