There is complex artwork involving type in your document. Depending on the complexity, Illustrator may not be able to handle saving this artwork.
Apparently PoS software in this regard. Save partial results now and then. At least you won't lose all.
Alex
"There is a cult of ignorance in the United States, and there has always been. The strain of anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that "my ignorance is just as good as your knowledge."
-- Isaac Asimov