HA ! I figured it out...
I started exporting and testing more and more of my scene in a new file...
It appears that Maya paint effects doesn't like to work with Maya fur... the character in my scene has fur for hair...
When I deleted his fur feedback node and tested the render... the paint effects plant rendered fine...

I wasn't aware that they could not be used in the same render.. I guess I will have to do an additional render and composite the fur over the rest of the scene in post...