As it turns out, The Sims, is a 32bit program that only allows itself to use 2gb of VRAM. Once you reach that cap it will shut off. I.E. send you to desktop. Users have been able to fix this problem on a PC (
www.soulfulsims.com) and it has worked for seemingly everyone who has tried.
I am on a mac, and I am trying to figure out a way to get this working on my OS. So if we can figure this out we might have a fix on our hands.
Google "Sims 3 LAA" or "Sims 3 Virtual MEmory" for further confirmation.
--Slickster