Temporarily move your Downloads folder to someplace else on your computer.
Then launch the game and see if the problem goes away.
If it does, then there is something in your Downloads folder in conflict or else incompatible with your installed game(s).
If you have ever downloaded any custom lots, it is possible one or more of them included (and installed) some questionable cc or a hack which you were not aware of.
Time consuming, but tried and true method for ferreting out problem file(s) in Downloads folder is the 50 per cent method:
http://www.sims2wiki.info/wiki.php?title=Game_Help:Finding_Problem_Custom_Content#The_50.25_Method