Thank you. I was able to reproduce on my machine. This example file is Sorenson Video 3. It would appear that this codec is not threadsafe. Here's one thing I found when googling [quicktime sorenson thread safe component]
http://lists.apple.com/archives/quicktime-api/2007/May/msg00202.html
I am not familiar with how Sorenson Video 3 relates to "Apple Sorenson" which is allegedly threadsafe according to the chart in the earlier link I sent, however this codec doesn't seem to work.
After I exported the movie to Photo-JPEG (video), AAC (audio), it loaded fine with asyncread.
So, AFAICT, my analysis remains appropriate to the reported problem. However, if someone can provide an example movie file which in theory should work (or definitive documentation or evidence that Sorenson Video 3 is in fact threadsafe), there may be some other problems. Keep in mind that the audio component, and perhaps additional tracks (like text/subtitle tracks mentioned in some of the asyncread threads) also need to be considered regarding whether or not the movie may be loaded in a background thread.
-Joshua