I don't know if this is caused by a bug in the game or if there is a software fix for this, but a complete freeze of your whole system could be indicative of a hardware issue. When I had similar issues in the past it was often an issue with the RAM modules. sometimes just swapping them around helped. It could also be that your GPU or CPU overheats, so have a look at the temperatures while the game is running or try the game with the case open and a fan blowing into it to cool it.