Hi Pete, err . . . again: with the very same quality settings, but with 4 lights less (i.e. 21 lights instead of 25 lights), the image rendered perfectly fine in about 5h, two days ago. I don't see how 4 additional lights (120% increase in light sources) will result in 135h total rendering time (2700% increase in render time), especially considering we've already had 21 lights to begin with which took the abovementioned 5h to render. ;) I know very well how vue's percentage, time estimate, and render steps work. As mentioned before, the first pass took close to 5 minutes, but the second pass, rendering about 10 lines of no-transparency, no-reflection, no-softshadowed textures, didn't proceed further than 6%. I don't know whether these 10 lines took 7h or 5 minutes to render, as I was in bed by then already. My guess would be the later, and looping for close to 7h afterwards. It's not as if I weren't used to 12h+ renders at high quality settings. But, again: 130h? If almost the same scene took 5h, previously? Clearly something fishy here. Are we really talking 5 days rather than 5 hours, due to 4 additional, no-shadow lights? Oh, btw, only one light actually casts shadows to begin with, the rest are fill and bounce lights. Even if the additional lights would increase rendering time by 2700%, this still doesn't explain why already the second render pass took 7h for 2 additional percents--corresponding to about 10 scanlines--when a similar scene was fully rendered including FSAA in about 5h, before. But that's not really the point of this thread. We've got the other one for perfomance questions. :) This is a thread about how to diagnose lock ups or dead loops. The render I mentioned was only supposed to serve as an example, not as a problem to be solved--if it takes 100h to render that image, fine by me. :) But: I am still wondering how to GENERALLY diagnose loops of death if they occur. Will Vue crank CPU usage up to 100%, will it simply crash, will it interrupt a render automatically (as it should)? Error messages? Any idea? ta, -Sascha.rb