Poser 2012 7G RAM. What is your minimum shading value set at? Default for all groups is 0.2. If your render setting is higher than that-it will use a higher value. I wanted to get more fine detail on skin and used a Python script to set the group value at 0.01. Unfortunately-I also ended up changing everything else to 0.01 as well. This uses a lot of memory-and I kept having the same issue you are reporting,

I went in and manually changed it to 10 for the Envirosphere and 0.1 for V4. My render now finishes.