Whew, I'm logged in after ages of absence 'cause I cannot ignore a fellow sufferer.
After years of playing with an Nvidia Geforce FX card (and in-game graphics blurry as hell) I can only tell you that there are far too many variables in this mess to determine the actual issue easily:
Driver version, driver settings, game graphics settings, you name it.
It's not enough that every computer is different: It seems that any new driver installation behaves differently, not to mention the settings of said driver.
Nevertheless, I found this at MTS2:
<a href="
http://www.modthesims2.com/article.php?t=97876">
Use with caution, because the newer EPs are not regarded in this article! You could end up with a nasty triangular/spikey mess in-game.
The moral might be that an Nvidia card is very likely not be the best solution for your game in the long run.