Karen, I am practically reduced to tears at the amount of help you are giving me. Thanks so much! You mentioned xp system restore - don't have a clue what that means. How do I do that? I render with p4 engine, and I do use extra heavy lighting, but the point is, I can go back and re-render a file that rendered fine a few days ago, only to have it lock up again mid-render. I am off to chase down these links you provided. Thanks.