Also check the number of undo's.  By default, Poser places it at 99.  Lowering the undo numbers to a reasonable number as well as clearing the undo cache can free up resources.

With 32bit versions of Poser, I have found that if I have been working for a couple of hours, it helps to save the scene, clear the undo cache, close Poser and wait a couple of minutes and then restart.  This often frees up resources.

I also found that keeping the number of other apps running in the background with it to a minimum helps too.