If you play with mods in your game, what I might suggest is removing all of them from your download folder. You can just cut and paste them all to a separate folder and put it on your desktop, or anyplace you can find them easily outside of the downloads folder. Then run the game as normal, enter a lot, and see if you get the error message. If you don't, shut down the game and add 1-3 mods back into the DL folder, then run the game again. Repeat this process until you get the error again. Since you're inputting the mods back in small batches, you should be able to find the culprit and get rid of it. Depending on how many mods you have (And if you're like me there are hundreds...) this might be a time consuming process. But a lil' patience should help you find the problem and fix it.
Now if it turns out NOT to be a mod, but rather a bad mesh or lot causing the error...removing that is a little trickier. In the event it's a bad piece of CC and not a mod...
http://www.modthesims.info/wiki.php?title=Game_Help:Finding_Problem_Custom_Content...click on that link and follow the corresponding links to help you along, and good luck trying to find what's frakkin' up your game.
