Keep in mind that especially when using multiple figures, each and every texture bitmap must be uncompressed to its full color and size resolution - times however many figures, and probably times each material zone for each figure.  You can try reducing texture map sizes before rendering (simply back them up, and then scale them down in some image editor).  For distance shots you may not even notice the loss of texture quality. 

Poser 6 is also pretty bad about bloating up on memory usage while rendering.  Poser 7 is a lot cleaner, but if your process gets above around 2.5GB it still tends to blow up and die.  This is the big advantage of 64-bit operating systems and render engines, because you don't have that 3GB process size limit any more.

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