I don't have texture filtering turned on, (apparently I have not enough memory) and I am using Poser 6. As for ALL of my renders, it's just most of them. A couple of times it has just "decided" to work, then after one good render it returns to being naughty again.
Anyway, here is a screenie of my render settings. I have used the exact one for quite a while, with no problems.
http://i74.photobucket.com/albums/i266/Sonita_Bonita/Pics_for_teh_webs/RenderSettings.jpg

And a render in one light set.
http://i74.photobucket.com/albums/i266/Sonita_Bonita/Pics_for_teh_webs/Seriously.jpg

The same thing in another.
http://i74.photobucket.com/albums/i266/Sonita_Bonita/Pics_for_teh_webs/Seriously2.jpg