Corona Volume Grid Problem

[mattspaeth]

These two images are the same frame. The one with the volume working is through Interactive Preview. The other is through Picture Viewer.

I don't understand why the volume is not working with the Picture Viewer. Corona is set to the render engine under Render Settings.

[mattspaeth]

I thought this may be an issue with the camera being inside of the vdb, but that's not the case. I'm consistently not able to get the volume to render in Picture Viewer, no matter where the camera is. Yet it works great in the Interactive Render window.