I have that problem all the time if I use more than one figure in the scene or if I use a single figure and a lot of props. I almost never use the firefly render any more because of that. I have alt-ctrl-delete to shut poser down that is the only way to stop it. I once let it run for almost 48 hours and it didn't progess any futher than about half way. what is funny is that it never stops in the same place twice. Also, I can render the scene using firefly and it will work fine. Then I change a pose and that's all I do and locks up. I have a P4 dell computer running windows xp with 1 gig of ram memory....