...I can’t speak for the morphing issue as I rarely use more than two figures in a scene and don’t use any Elite textures or morphs. However rendering and viewport ills are something I am all too familiar with.
As someone who works within extreme memory limitations (2GB useable out of 4 as I am in 32 bit) I resort to a number of tricks to ease system load while rendering. While I predominantly use Daz Studio4.5, I also have, and work with Poser Pro 2010.
One of the issues I frequently experience with Daz4.5 is the viewport going grey if I make to big of a morph/transition slider adjustment or camera move when I am working on a scene. This is not so much memory as it is OpenGL related since my system barely meets the application’s minimum OGL requirement. What GPU do you have, and what version of OpenGL does it support? While the “minimum” rating means the app “most likely” will work, the optimal rating (I think 2012 lists that) is recommended for essentially “trouble free” operation.
I also learned that sometimes one thing (like having three M4s) works OK in once instance and doesn’t in another. A lot of times it has to do with the particular scene elements (props, lights, backgrounds, hair, clothing, etc). For one, I notice there appears to be a lot of reflectivity in the scene. The satin drapes, the leather clothing texture, the leather chair, the window glass, and quite possibly the paneling and floor if they are supposed to have that “polished wood” look. Next, there are the transmaps and gloss of the hair which require extra calculations and thus add to the size of the renderfile. If you are using ray traced shadows, you may also want to check your ray depth, as the higher it is, the more calculations that are required as well.
So quite possibly it could be the combination of all these things in one scene that, while individually may have rendered OK, but together (along at the pixel size of the final rendered scene) could be more than your system’s available memory is able to handle.
Sometimes it may also be just one small thing.
A while back I had a scene that used several wall segments and the floor of Jack Tomalin’s Baroque Grandeur which kept crashing at the same point in the render. After trying a myriad of fixes, which included reducing the set’s texture files, having the render engine ignore the transmaps of the hair, and changing from ray traced to mapped shadows, I discovered it was the reflectivity and refraction index (both set at a default of 100%) of the hanging crystals on a lamp in the background. A very very small, almost insignificant component but one that my system just didn’t like. After I turned the settings down, the render completed without a hitch.
While time consuming, I would check the surface settings of all the elements in the scene
I look at the texture sizes of scene elements. Anything that is in the background will not suffer visually if you reduce the texture size in a 2D app like Photoshop or Gimp. Of course you have to save the reduced texture image under a different name like say “[texture name] small.jpg” so it doesn’t overwrite the original one.
I never render to the active viewport. In Daz Studio I render directly to a file. In Pro 2010 I either render in “Background Mode” or do so through the Queue Manager.
Prior to rendering, I switch the viewport to wireframe view which also reduces the “memory footprint” of the scene file because the system doesn’t have to devote RAM to displaying the textures, lights, shadows, and other effects.
If all else fails, there is always the option of rendering in multiple passes, say one figure at a time, and compositing the scene in a 2D app. While it is more work on one hand, it would minimise if not eliminate the chance of the render process crashing because the render file would not be as “heavy” as it is with all three figures. This could also help avoid the morphing crosstalk ills you are experiencing with the one character standing behind the seated one.