I think there seem to be certain points on the map that cause the game to crash, I gave found several since restating the game, I have returned to the same point on the map & it always crashes at that point, either they did very little testing before they released the game or the beta testers they use are rubish.
I could be horribly wrong here, but you may also be experiencing the same problem as I have. You might want to try starting a new character, disabling all autosaves and heading to the areas where you experience crashes. My knowledge is severely limited, but there is something to do with a save corruption which causes crashing in certain areas. I had a consistent crash at exactly the same point when trying to get to the Thorn every time, and I was only able to fix this by starting a new game. You might want to give that a whirl, just to see if it works. If it does, keep autosaves disabled and make good friends with your quicksave button