These drivers are being served up by the nVidia website for Vista/Win 7 64-bit variants.

A warning: If you are using an ‘Ajax’ based start page like Pageflakes or the Sympatico/MSN customizable start page, you will experience very bad flicker as you scroll across or down them.

Do NOT roll back the driver. Uninstall it in its entirety and replace it with an older version. I am using 186.18 which is OK.