Have you checked who the father is to see if it makes sense? Maybe she is pregnant by aliens.
Actually, I didn't check that. I should have, but it was really late at night when I decided to just give up and terminate the pregnancy. I don't have anything that would allow her to be alien pregnant, and she hasn't been kidnapped. Her brother was, though, and I haven't played her house since his pregnancy and his daughter's birth. I wonder if some kind of code spilled onto her.
I got the house to load, but I still wonder what was wrong with the pregnancy that caused the birth to freeze the game. Not to mention that she shouldn't have been pregnant in the first place.
ETA: I just read your post in the testing grounds thread. Can your Sim give birth, or does your game freeze when that happens too? It does sound like the same issue.