Follow up question:

I'm using Mental Ray to render. When I try to render from the command line or by right-clicking the file in windows explorer and selecting "render" it's defaulting back to the Maya Software renderer.

I've changed my preferences to Mental Ray being the preferred renderer. That didn't do it, it still wants to render using Maya Software.

Is there a way to render from the command line--or in other words WITHOUT opening Maya--and have it use the Mental Ray renderer?