Sims 3 causes screen to go black and lose signal.

I have been playing Sims 3 on my computer for over a year. In the past month it has been causing my screen to go black and lose signal and the only way to recitify this is to hard turn off the computer. I have updated my graphics driver, defragmented the computer, updated Windows 7 and reinstalled the game. I have tried reducing the graphics on the game but it doesn't give me enough time to enable the changes as the screen goes black before I can save changes. I have checked my system after the computer has restarted and it doesn't acknowledge that there was a crash problem in its history so I cannot find out what caused it to happen. My computer and driver are not  overheating and my computer is compatible with the game as I was playing it for ages before this problem happened.

Any help would be gratefully appreciated as like I've said I have tried everything! I really want to be able to sort this as I can't be bothered to buy any more Sims until I can actually get the game to work!

Thanks in advance