If you open a pre-Maya 2012 scene in Maya 2012/2013 without the mental ray plug-in loaded, you may get file load errors.
Before Maya 2012, mental ray attributes were static attributes. Therefore, it was possible to set and save these attributes to non-default values without saving a dependency on mental ray if mental ray was never used as the renderer.
Beginning with Maya 2012, mental ray uses extension attributes. Therefore, when this file is loaded without the mental ray plug-in loaded, file load errors occur that indicate that these extension attributes do not exist.
If you are not using mental ray to render your scene, you can safely ignore these errors.
If you use mental ray to render your scene, you should ensure that the mental ray plug-in is loaded before you open the scene file.
