Based on a cursory look at the backend code, I think you may be nearing the limit of your available memory while compiling. If the game is sufficiently complex and you have a relatively small amount of memory (which is likely to be reduced significantly by an OS like Vista), that could cause some problems. More information would probably help, but I bet there's probably little chance of properly verifying this issue since it's intermittent.

Hrm, that's an even deeper mystery then. It'll probably be hard to make any headway on this unless you can reproduce it somewhat reliably.

I'm not entirely sure memory could be ruled out as a factor though. While it's a long shot at an explanation, oftentimes very strange one-off events can be a sign of RAM failing. If you've been seeing any other weird behavior on your computer, that's something to watch out for. That's probably not what's happening here, but it's one possible explanation as opposed to none at all yet.