I had the same exact problem in my game whenever there was any steam, fog, or mist. Now, I don't know much of anything about video cards and drivers, but I went under the performance and quality setting for my video card. All the options except the 'Antialiasing settings' were clicked to application control. I rolled the dice and set the antialiasing setting to application controlled and I haven't had a single freeze or problem since. I have a Nvidia GeForce 4 MX Integrated GPU. This is the run of the mill video card that came with the computer, and as I said, it works fine now. I hope this helps your situation!