easy fix for poser 13.1 up 

just set the Atmosphere " Volume_Density " to 1000 this will speed up the render back to max, Do not turn it on if you use the Primitives as Smoke or Fog objects, save your setup this should keep it that way and you will not encounter other speed loss with textured models you have that might get in conflict with this error, as I am pretty sure that many other material and model setups are affected causing a render slowdown.