My Sims 3 game keeps crashing too. I have Windows 7 and it just started happening recently. I'll be able to play for about 30 minutes and then the box with 'Sims 3 has stopped working.' ect. will pop up and it closes the game. I feel like it's a problem with EA.
I just did some research, and apparently there's a program on Windows that will automatically shut your game down. Have you tried doing this:
1.) Go to your Documents/Sims 3 folder. Open one of the files that begins with xcpt in either WordPad or a similar program.
2.) Scroll down to the [exception info] section. If it says unknown module next to "address", then it was the Windows program that shut your game down. If it does not, check another of the files if you have any. If none of them say "unknown module", then something else caused the shut down and I'm not sure how to help you there.
3.) If it was indeed the Windows program that did it, open up your control panel, go to System and Security -> System -> Advanced system settings (on the list on the left side).
4.) Under the performance box, hit settings.
5.) Switch to the "Data Execution Prevention" tab - this is the program that is probably shutting down your game.
6.) Switch the option to "Turn on... except those I select"
7.) Add your Sims game to the list by going to your program files and finding TS3W.exe in the "The Sims 3" folder.
That ought to do it. You may need to restart your computer for the change to take effect, but hopefully that fixes your game.