sims 3: Can't switch between my sims

i go onto my game and i have two sims in my household, the two icons on the left hand side dont have their faces in them and are just green, only the bottom icon is selected and when i try to select my other sim, it doesn't change between the two so im stuck using only one sim, but even that doesn't work because when i tell my available sim what to do, she doesn't do anything. i've looked online for answers but i can't find anything, all i can find are forums that say that people have had the same problem and that they have tried to conact EA about it but they weren't helpful. i deleted my sim household and made a new one it was fine up until i shut it all down, when i went back to play it today the same thing happened again so i would like to know how to fix this as so many people have had the same problem. thank you.