Well, I wouldn't jump to that conclusion w/ no more evidence than that. Memory management would play a role there. If you need to allot more ram in your mac I would check that also. However, I will say this. Carrara's opengl is not what it should be (IMO). D|S is great (what I think OGL should be).  Here are some things to try to help. Maybe you have already done them all. Play with your preview settings maybe opengl won't work as well. If you use opengl turn off all the xtras like reflection, especially transparency, use current preview pane only. Opengl should be faster because it is supposed to be hw accelerated, but try D|S and you will see a huge difference w/ it's work environment opengl preview. It it is incredibly accurate and moves in realtime w/ almost no lag. 2 other things.
All that importing etc... leaves alot of trash in carrara so remove unused master objects and shaders religiously. I made shortcut keys for these 2 things. This can also clear up weird errors when saving. For me I know I will have to get more ram based on what I am seeing w/ the poser mesh models. I only have 1 gig. There is also the new texture cache option in preferences so I would maybe check that, also.

No need to think outside the box....
    Just make it invisible.