[Postman]

Here's a thought. If it turns out to somehow actually be related to 12 core machiness, I wonder what happens if you disable one of the processors (leaving you with 6 cores)?

How to do that? IDK, this from an apple discussion group:
Navigate to /Library/Application Support/HWPrefs and launch the CPUPalette program.

(If you don’t find it there, insert your Leopard install disc, click on Optional Installs, select Packages, and double-click on CHUD.pkg; that will install CPUPalette.)

It will display two graphs showing how busy your CPU’s cores are, and let you disable one or more of them. Click on the oblong button in the upper right corner to reveal a settings panel where you can adjust transparency, sample interval and history, and chart format.

Not sure if Snow Leopard works the same way.