Everytime i get ready to play the sims, my computer screen goes blank n im back to my main screen why is that?

I have the sims hot date on my computer and i always download objects from different websites. and it wasnt even actin up b4 but like now when i play its like, i'll build the house, n when i get ready to save it, it exits out n all my saved work is gone, and im back on my mine screen again. if its disk space i tryed to delete files i dont need and it still does it. can u tell me y i keep having this problem?