I believe your scene is just too big in memory required for Poser . Textures can be a big part of the memory required so its worth looking to see if you are loading many 3000 x 3000 pixel textures. 

The usual way I tackle these is to remove all the foreground props , and render the image , then reload the scene , and delete the background stuff, render  and composite the two images in Photoshop.

You may squeeze it in by render in seperate process because that will use a bit more memory.