Oh, I wasn't agreeing with taw on that. Just responding to your association of causation with metaphysics. I don't see Omega breaking any causality, whether in a metaphysical or statistical sense.

As for excluding backwards causation and causality loops -- I'm not sure why we should necessarily want to exclude them, if a given system allows them and they're useful for explaining or predicting anything, even if they go against our more intuitive notions of causality. I was just recently thinking that backwards causality might be a good way to think about Newcomb's problem. (That idea might go down in flames, but I think the point stands that backward/cyclical causality should be allowed if they're found to be useful.)