Hmm... I had that same problem, But the problem with me was that I was using a back-up copy that I downloaded from the web. I was able to play but when it came time to build something that was
disabled. (a new security protocol that maxis is using)
If you are truly using the retailed cd's I would contact maxis and ask them what to do in your situation. Also having virtual drives enabled can cause problems with game play. *Hope you figure it out*