The Sims 3 Has Stopped Working

Basically, I have Sims 3 (which I bought) and downloaded the "Katy Perry Sweet Treats" expansion pack, and it was all working fine. I then downloaded Sims 3 University, and ever since then the game stopped working? So I uninstalled the University expansion pack, because I assumed that must have been the problem, but no. The game still doesn't work??? I've tried running without custom content, and it still says "The Sims 3 Has Stopped Working". If someone could help me to resolve this issue, that would be great