"Sandra Bullock has entered negotiations to lead Alfonso Cuaron’s upcoming film Gravity after news just earlier today revealed that Natalie Portman turned down the leading role in the $80-million sci-fi epic. Variety states “scheduling conflicts” were her reason for refusal. This means that Bullock is set to play a woman in space trying to get back to her daughter after a disastrous mishap on her space station."
I was really looking forward to having Portman in the role. The movie sounds amazing and it's been a while since she's done anything sci-fi or action.