It's a memory problem, I think (though it's clear that Poser is violating processor memory canons or the exception would not activate). You could try eliminating shadows for all but your main light and setting that to raytraced shadows. That will save some memory. Try turning off shadowing for any objects that don't actually cast them (like the ground). Eliminate any lights you don't need and replace the ambient lighting by applying the diffuse texture at some fractional value of ambience in the ambient channel in the materials editor. Get more memory!