Running Mac OS 10.3.9 and Quicktime 7.3 here.
Motion Pictures 2.1.1 does NOT work. (I keep getting that Quicktime error message at the end of the render.)
After reading through the posts here I suspect that 2.1.4t might work (With the newest version of Quicktime), however, 2.1.4t requires Toast 8. (Even though I just bought the stand alone 2.1.1 from the Roxio site.) I don't have Toast 8. (And even if I added it, I would also need to upgrade the Mac OS.)
System Requirements listed for Motion Pictures is OS 10.3.9 and Quicktime 7 or later. Clearly I have that, and yet, it seems I've purchased a piece of software that is completely unusable on my system.