https://vimeo.com/41890082
Why does the flame only render when there is geometry behind it?
It is alpha channel 
Just turn it off.
the link does not work. i remember we had a similar issue when a non vray version is rendered with vray
Sorry. I fixed it by loading a preset. Real objects and smoke needed greatly different levels of illumination so I tweaked the Phoenix render settings too much. Should have just used separate lighting.