We’ve all been there. It’s annoying as all hell, but about a third of the time, Maya just won’t load the mental ray plugin, no matter what checkboxes you click in the plugin manager. And since the standard Maya renderer is about as effective as a fart in the wind, mental ray really ought to be the default renderer anyways.
So far as I can tell, there really isn’t one. Sometimes Maya just decides it doesn’t like to load your plugins.
The good news is that plugins are still handled within the framework of MEL, which means that it’s very easy to put together a simple script to load mental ray when you need it. Just type the following code (and watch the capitalization) into the Command Line in maya:
Highlight the text, and middle mouse drag it to an empty spot on a shelf. Hey-presto, you’ve got a one-click solution for loading mental ray whenever you need to. No more hunting down the plugin manager and checking stupid boxes that Maya ignores anyways.