5 poser figures in a scene...fully textured, Hmmm.
Let's do some math.
A 4000x400 texture uses 64 megs of ram (that's a fact), how many different textures are there in your scene, what's their resolution?
Did you import figures as single mesh? Did you check the "collapse identical material" box upon object import?
You have a drop of resources after an object import, does it prevent you from working normally on the scene? Do you get warning messages about low resources? OOMs?