Possible reason for the lock up while rendering if that is the problem I have found is a corrupted prop and texture map. To diagnose if this is the problem is to load each chartacter one at a time and the render it each time. I found this has helped me diagnose similar situations as to why Poser locks up while rendering.

If you experiencing this as a persistant problem you may need to ditch your excisting runtime library and re-install each item one at a time.