well for the first thing I see is that you only have 100 megs of ram partitioned for bryce..1 good object will take up that much when you have terrain and extras..I also agree with the lighting and textures but that all is a mute point if you have volumetric settings set on in the clouds/sky editor check to see if you do and if you dont do this then...save your object into the user presets for objects...2.then export your obj to a folder(where you know the obp file will be put and you can get later...3.export the object into folder..4.re-import the model back into Bryce and re render....now hope that helps when I had 1 of my military bases I was building for Alamo did the same thing so I did what I told you to do and it worked everything was fine went from 2.5 hrs down to 18 minutes with scene...HOPE THIS HELPS