Despite the 64-bit environment on your computer, Poser 10 is a 32-bit program and is subject to ram memory llimitations.  Expect, at least, 3 GB of memory usage.  

But "out of memory" does not necessarily mean you are literally out of memory.  There are other problems which may impede it's function.  Are there other processes running in the background?  Are internet browsers active during rendering?  How populated is the stage in your scene?

Certainly, using lower resolution for both background figures and textures will reduce the render load.  If you can medium resolution, do so unless you are doing closeups.

 Raytrace or depthmap lighting?  

Prominent transmaps for many of the models in the scene?

Are you using IDL?  What are your render settings?  Are those significantly high quality?  Raytrace bounces and reflective surfaces, are those present in the scene as well?

Rendering in a separate process?

There are a significant number of combinations which can cause out of memory; I just mentioned a few.