We need to know a bit more about your situation in your saved game, your PC settings, etc.. What we have now is the barest of info, and makes it really hard to narrow down your problems besides the crash at 4/24 ingame.
Did you get error info box that popped up and what did it say? Did it lock up your system so that you had to reboot? What else were you doing at the time? There are so many issues that could be the issue, we need much more information please?
Thanks!