well, I'm not particularly OSX savvy on the details, but I think the issue has nothing to do with your hardware. The one thing I'm not seeing in these threads is anything that would let me duplicate the issue to monitor the performance hits (albeit on PC) and spot the potential culprits. What is the set you are using? There are several architectural sets out there I wouldn't use becuase they are, bluntly, too damn large -- in polys, that is. There are some out there that look pretty nice but come in at a couple hundred thou polys each, and they each have gargantuan textures. The mem load on them alone -- jus the set and the textures for it -- is close to 2 GB. Add in a V3 plus a "hi-res" body texture and v3 hair with a hi res texture and you're talking a need for possible two gig more Ram. That'll cap out a windows system. Since I like to render anims with about four figs on average, I don't load these sets because they do me no good. I'd suggest looking to the architectual model you are using, the size of the textures for it, and the textures for the other elements -- reduce them and you'll likely see better performance.

thou and I, my friend, can, in the most flunkey world, make, each of us, one non-flunkey, one hero, if we like: that will be two heroes to begin with. (Carlyle)