I am running AE 9.0.2 on a Mac Pro running Snow Leopard - although I have had the following issue before installing the new OS.
In rendering compositions as QuickTime DVCPROHD 1080i60 files, every so often, and not consistently, I get noise/static for one frame on the video. Like I said, it is difficult to replicate. When I rerun the render, I either don't get the noise, or it occurs in a different location, or not at all.
I am using Magic Bullet Looks as well on these sequences. Running a test now to see if that makes a difference.