I know the scene file is heavy, not so bad with hardware texturing turned off. Anyhow, no i didn't turn auto exposure off, i'm not going to re-render that animation, it was just a little learning project. I will turn it off if i'm in the same situation in the future and see if that helps.
I did think about the fog causing the problem. I could remove it and re-render it just to see if that is the problem, i'd like to find out. Then again it could be auto-exposure so that would need another render just for elimination.
I think i'll keep your ideas in mind for my next project and see if they help. I'm lucky im getting the opportunity to spend a little time with Maya, i don't want to be sitting around too much waiting on 16 hour renders!
Thanks for all your advice.