I see...thanks, Rutra!  It ended up crashing on me anyway - I'll try re-loading the scene and rendering again with the exact same setting to compare render times instead.  As for Vue 6 - I was going to get rid of it anyway.  I purchased Vue 7 Complete as a sidegrade from Vue 6 Infinite - I only had Vue 6 on my computer until I worked out if Vue 7 would work properly (for some reason I couldn't download the Pioneer version to try it out).  Now I know it;s all A-OK and working, I'm going to get rid of 6.  Thanks for the pointer to thread, I'll have a thorough read of that.