Sean,
I'm not sure why, but the motion blur lesson is touchy on my Mac. Sometimes it crashes. If you move the file it can't find a bunch of resources . . . which is weird since they should all be packed if I'm seeing things right.
I unpacked the .zip again, and it sees the jet, but it does not see the tree image.
It wouldn't surprise me to learn Blender was caching something and got confused when I put this in the "My Work" directory, trying to preserve the original file, but I thought I'd mention the issues I had.
