@musicshaman -- Are there leaks or drafts in your attic? That could make it moist enough for mold to grow. Or it could be stuck in your insulation, and just have grown out from there.
I read that certain types of air conditioners can cause your attic to be more prone to mold too.
I don't know about the respiratory symptoms, man. I know that mold can cause problems like that, but I'd say have your doctor check it out to make a real diagnosis.
If the mold is the problem, they give you an allergy medication and problem solved. If it's not, at least you can rest your mind about the mold. Win-win situation.