we have created a new build of the NVIDIA Mental Ray for Maya plugin, version 1.2.1. The primary purpose of this update is to fix a problem with the original installer, which stopped working with latest NVIDIA driver installers on Windows. At the same time, we also addressed few minor issues in the plugin itself, and in the Mental Ray core engine.
You can download the new version from our Mental Ray for Maya Forum for Linux, Windows, and Mac. This update is not auto-distributed through the NVIDIA Professional Application Center this time.
We would appreciate if you let us know that it works for you.