Apple Shake crashes with optical flow & new multicore MacPro

Hey there,

I've been working with Shake for years, on powerPC G5, then on intel macpros. I've been thru the 10bit PRHQ turned into noise with 4.1.1 update. I finally had a stable usable 4.1.1 version that ran perfectly on a 8core 2008 macpro, running latest 10.5 OS.

I've just bought the double 6core 2010 macpro, that runs 10.6. Shake is even faster, and I can multiply parallel renders, that's really cool.
What's less cool is every time I ask for optical flow module, Shake crashes immediatly.
I have to use older machines to deinterlace or convert footage, and that is really not cool at all...

My question : Is it a problem with OS version, or with hardware ?
I runs smoothly Shake on intel 8core macpro without a single problem, but it is 10.5, and I guess I can't downgrade my 2010 macpro to 10.5...

Is there any workaround ? Will Apple endlessly mute about Shake ? Do I have to simply trash one of the best software ever ?

Thanx for any help,

David