Hi guys,
Please make sure you have taken the time to optimize your system performance by reading through this thread and performing all the steps mentioned within.
This game is intense and if your computer isn't up to snuff you will experience the occasional stutter or freeze. Sometimes just having the huge spec numbers on your PC is not enough. If you have a lot of unnecessary programs running like many store bought PC's have (extra browser windows, printer configs, tons of start-up programs, Anti-Virus software) they will detract from your performance.
Please make sure you've taken all the steps you can to optimize your system including playing in a smaller window, lowering the graphics settings in the game options (biggest reported help) and turning off some of the "extras" like water reflections. Every little bit will help.
Good Luck =)