If your specs meet the requirements, could possibly be down to your GPU overheating, a driver issue etc. Make sure you're using the latest graphics drivers (my crashes went after i changed from Catalyst 10.6 to 10.9 fyi), and your machine gets enough airflow. :)
I dont want to put a downer on this whole topic, but the links other people have posted contain mainly PCI-Express cards (haven't checked all of them) which will NOT work in a PCI slot, just so you know. Anything from the Nvidia 6000/7000 series will run FM ok plus some cards from that series...