Have you done the usual stuff to reduce lag? Make sure the game is regonizing your graphics card, increase the texture memory it can use etc, etc. I used to have a problem with crashing, but after dedicating more texture memory to the game it never did again.
Nraas storyprogression may lag your game to oblivion if your PC is old. What sort of lag do you have? If you have pie menu lag (lagging when clicking on sim) a lot of store content causes that.
You should always have v-sync on for it because TS3 does not limit FPS -at all-.
