System Crash on every render! _CS6

Question

just bought a brand new Mac Pro. 12 core (2012 5,1) that crashes every single time i render anything in AE CS6 using the queue. i've worked in these exact same project files on my old quad core (3,1) and had no problems whatsoever. i'm literally opening the same files.
if i activate multiprocessing in preferences *at all* my entire system will crash after every render in AE. i've tried several settings from 80% dedicated to AE all the way to 80% dedicated to "other apps" and everything in between. the only way to render out a project file using the queue is to first turn off multiprocessing. which obviously causes render times that remind me of the 90's.
i've found quite a few people in different forums (including here) experiencing the same issue on the newer multi core machines. i've heard theory's but wow, this seems to be a tough one.
the funny thing is i can work in AE with 50gb assigned to it and the other 14 to the system (and let me tell you it SCREAMS!) but i HAVE to turn off multiprocessing and restart before rendering anything? i've read about rumors with quicktime (specifically H.264 codec) and using v7 as opposed to X but i render from other software with the exact same codecs and no issues at all. and in fact it doesn't matter what codec i use to render from AE. same result. kaboom!
as far as specifics, like i said i'm working with the exact same files with the exact same plugins i created on my 2008 mac pro and never had an issue at all. also i 'fresh installed' CS6 and everything for that matter. no copying from the old system. those wondering about having 2 GPU's, that was my first test. pulling one at a time and seeing if that made a difference. nothing other than some performance stuff (not related but really great results .. if you want to message me i'll fill you in). checked the crash report, not memory (crucial brand). and i REALLY want to point out, it's not just AE that crashes it's the entire OS. not a kernel panic but everything just freezes and i have to hard restart using the power button.
is there a workaround anyone has found yet?
i tried using dynamic link to render in Premiere but it didn't recognize one of the plugins used and rendered without it.
for those who might have set-up questions.
64 GB memory - Crucial
3 internal Crucial 500 GB SSD's. 1TB Western Digital running the OS
ATI 5770 & Nvidia Quadro 4000 (i've tested every combination with regards to this to eliminate it as a possibility)
After Effects CS6 [11.0.2.11]
quicktime X and 7 installed

Answer 1

Figured it out! *fingers crossed
While troubleshooting to further narrow possible causes I imported the AE Comp using dynamic link in Premiere. For the record it rendered using QT/264 just fine.
But there was a clue in the .mov file when I viewed/tested the results! One of the plugins used was disappearing a reappearing throughout the scene. [Plexus 2.0.6, by Rowbyte]. That prompted me to go back to AE and as my grandpa would say "fiddle around with some stuff".
I won't bore you all with the details but I finally just created a new project and started from scratch. Everything is working fine now. Actually better than fine, this thing is flying! I have NEVER seen AE run so fast. I dropped geometry in there, applied Plexus, added cameras, DOF & some animation and it's playing back in real time without caching! Attaching my settings:)
(it appears AE is using both GPU's?)