ok before I put this into tech support I want to see if anyone else can replicate this:

I load P7, load in a mesh, with render as seperate process ticked I render to a blank screen
I goto Zonealarm, enable Poser to have full rights through the firewall
I hit render, everything works perfectly.
a few minutes later I hit render and I'm back to the blank screen again. no settings in the firewall have changed.
I have both Poser.exe and ffrender.exe at full rights (all sections ticked and set to super)

tried allowing (as per advice given before) 127.0.0.1 for each process so they have a clear path. rendered once no problems, then returned to the blank grey screen on the next render.

and then it gets strange. the area render works perfectly, but the full render blanks out.