Morgano, have your tried rendering with the Poser engine, not Firefly engine ? How does that work out ? 

You can also try reducing the texture sizes in the Render Options menu in for the Firefly engine, but sometimes that gives a pretty cruddy result. 

Have you also checked in the Material Room to see whether there are any un-connected shader settings which you can remove using the menu options.  Clean up all the dis-connected shader items for each material zone of each prop.  Sometimes, too much un-linked rubbish accumulates and causes Poser wit get a headache.

 

 

Eternal Hobbyist