If you don't use ray tracing the image size shouldn't matter much, because the rendering is done bucket by bucket. But of course a bigger picture needs more memory for storage, so that could be a part of your problem.

I had similar problems with Poser 6, my problem was that I had ony 512 k memory. If you can, upgrade your memory to 2 GB, that should help. Updating to Poser 7 would probably help too, since P7 handles textures in a very different way. I could render bigger pictures on my laptop after the upgrade, and quite a bit faster too. On my main computer things did not change that much, but then it had 2 GB of memory - enough for my small scenes.

One more tip: go in the hirarchy editor before rendering, and click visibility off for all body parts hidden below clothings or props. No need to waste memory and computer cycles for Vicky's hip and legs when you see the pants only.

Hope it helps a bit.

A ship in port is safe; but that is not what ships are built for.
Sail out to sea and do new things.
-"Amazing Grace" Hopper

Avatar image of me done by Chidori.