Been there done that
You can disable the face function in preferences. I did such, and no change. It still sucked all the RAM up in a matter of one minute. I also made sure my iMac with 4 GB of RAM, and 10.6.2 was running at 64 bit. Looking at many other forums today I noticed many, many others are have the same RAM hog problem with Aperture 3. No one seems to have an answer that works. This seem to be innate with Aperture 3. Surprised that this wasn't noticed by Apple in beta testing before its release. 😕