I agree with you on the instability.  I have had old files crash on 6.2 as well.  I don't think I have ever used the replicator tool, but my bane seems to be refractive and reflective semi transparent objects like some kinds of glass and crystal.  I am really amazed that the ocean water shaders don't crash it.  Usually removing and recreating some objects allow it to render properly but it is very hit or miss.  I am completely self taught on Carrara, beginning with the old Ray Dream program.  I don't have the cash to outlay for another 3D application so Carrara is it for me.  I also am getting a bit too old to start from scratch, learning another more complex package.  I am disabled now so my only means of income is going to be the models I can do and sell in the marketplace.  I have only gotten good enough to produce commercial quality models in the last few months so again, spending years learning a new package is out.  You know what they say about the devil you know...  I can usually get Carrara to do what I want, even if it takes a few stressful hours to do so.  I am lousy with the vertex modeler so I stick to spline models.  You would be amazed what you can do in there. :)  Maybe one day DAZ will correct the memory leak, and all the other little annoyances that hamper the creative process.  Amazingly the model lighthouse I have in the marketplace here is probably the most complex model I have done to date, and it is one of the few that rendered flawlessly and relatively quickly on the first try, without a lot of hassles.  I guess that C6 is finally starting to like me :).