I imagine it’s a bit late for consolation on your project, but I can say I’ve actually just run into this myself. I had XDCAM EX footage I was using for greenscreening, and then planned to bring the keyed shots into more complex compositions. To save time (I thought) down the road, I did my keys and then prerendered the key comps. Lo and behold, when I looked at the prerenders, half of them were freeze frames. It was weird, because it was not consistent – some of the prerenders worked (they moved) and others were still. When I went back to look at the comps I had made the keys in, again, some of them moved, but all of a sudden, others wouldn’t refresh – the footage itself had become a freeze-frame. When I went out to the footage viewer, it was fine – it moved. As soon as I dragged it into a comp and applied any effect or transformation or mask, it became a freeze-frame. What’s weirder, is that the footage had been moving when I made the keys (I needed to animate masks, so I know things were moving then), so it wasn’t always this way. Things just started going crazy when I did some work, went away from the application. and came back and did some more work.
So I found this thread and suspected codecs, and I’ve now gone out of AE, converted my XDCAM EX footage into None-compressed, and brought the new clips into my AE keying comp. It works. For now.
I sort of suspected perhaps my computer went to sleep during the prerenders or just while AE was running, and I’ve definitely noticed CS3 hates when it is open and my computer goes to sleep. I’ve had numerous crashes and freezes (Mac OSX 10.5.4) from waking a computer while AE was still open. So there’s a couple of potential culprits.
Reynolds, any discoveries at your end in the meantime? Does this sort of conversion help your stuff? You’re right – this must be happening to SOMEBODY else out there.