Ok, a bit of development here.

I did a scene optimization and now it wont batch render any of the frames.

It starts and then stops without doing anything, and this is all I get.

Image name is now BIN_PAN_
// Result: saving temporary file E:/Media/Maya Files/Projects/Still_Moving/scenes/BIN_PAN___3592.mb //
// Result: Rendering with mental ray... //
// Result: Rendering Completed. See mayaRenderLog.txt for information. //

I will have a look at this render log and see what it says.

The plot thickens.