A few days ago Nvidia released the v2.41 nForce mainboard driver, later a newer driver came which was supposed to fix problems in the original release.

But now Nvidia has concluded that there are so many problems with the v2.4x drivers that they have been removed from their site, and Nvidia recommends you to revert to their previous v2.03 driver release instead.

Instructions on how to revert to the old driver are here.