My MentalRay is a plug-in. Not sure whether that means it is stand-alone or not. On the Mac there is something called Activity Monitor, which I have been watching while batching and experimenting with various combinations of threads and auto memory. At 16 threads and auto memory I was looking at 70 minutes, at 8 threads and 9900GB memory I was at 50 minutes but I was getting dangerously close to running out. My next attempt (in batch) will be 12 threads at 8000GB.

As for the render window, it is still not playing nice (stopping at about 10%). In the little rendering progress window (just below the MEL scripting line) something like "MentalRay memory low. Aborting", appeared for just a few seconds and then the rendering stopped—but NO error message in the log. I decided to go for the settings listed above erring on the side of caution I went with 7000GB and hit the "redo previous render" button. No go.

Now I move over to the logs at /username/Library/Logs/Maya/mayaRender.log and there's nothing there. The last piece of log info is from yesterday. Now I'm really stumped.