I am using Vista 64-bits, Poser 8 SR1, have 4GB of RAM, and I always try to leave task manager open with the Performance tab selected where it shows RAM and CPUs usage. Thats actually how I know it crashes sometimes: all CPUs are steady at 0% activity (because when rendering using "Make Movie", you cant see whats being rendered).

The RAM usage starts usually at 2.7GB total, and goes up, up, up... until it gets to 3.81GB. Then it oscillates there between 3.81 and 3.75, and eventually it'll crash.

Btw, mostly it will only crash on scenes where the camera is poiting to the horizon, where you can see the ground fade away (even though the ground isnt that big, its usually the actual size the GROUND object comes in Poser). So the same scene that crashes, if I just move the camera to an angle where less ground is showing, it will not crash. I do believe this is indeed related to RAM usage, as it many times crashed with that window saying its out of RAM, and also in the past I got rid of this problem by putting more RAM (from 2GB to 4GB).