I have installed the game but it won't start. Online, it syncs the cloud and then nothing. Offline I just get nothing.

Have you already tried this?

http://answers.ea.com/t5/Mass-Effect/Mass-Effect-won-t-start/m-p/282278

If that does not work for you, please give us a little more detail on your issue. This is a nice guideline:

http://answers.ea.com/t5/Mass-Effect/How-to-deal-with-tech-problems-and-tech-questions-the-report/m-p/317302