software for sims stopped loading

I have a macbook that is from 2008. it is running lion. we just gave it to my daughter for xmas, she wanted to play sims on it. we have downloaded all of the sims 3 games, which still leaves a lot of room on the hard drive. the game was working fine, and now will not load at all. We also have an issue with the screen not working unless it is in a certain position. any clues on how to diagnose or fix??? Not very familiar with the mac at all.