Well, I'm now having much bigger problems.
So it turns out I had actually updated Toast on both machines. 10.0.3 is working on the 10.5.8 machine, not the other.
In any case, I created a Blu-Ray disc by dragging in files on the 10.5 machine. I dragged in the .avc's, and the audio with the same file names then appeared as well. There were two .avc's. One, a simple 10 sec. of black used as a spacer. The second, my niece's wedding. The spacer had 5.1 .ac3 as the audio, the wedding has only a stereo .aiff. I set the disc to auto-play. Then I saved it as a BD disc image. I then brought that over to the 10.6.1 machine, and burned the Blu-Ray disc from the image. I thought, whew, at least I can do it.
Unfortunately, this is what happens. The disc, instead of auto-starting from the black spacer, which is the first file, starts from the wedding -- so no spacer. It turns out you can only get to the spacer when you go to Menu, then both files appear as different choices. Why is it starting from the second choice??
But worse, there's no audio for wedding. I can't tell if this happening with the spacer as well, since the audio for that is simply silence.
Sorry, I don't mean to beg, but I'm kind of getting at my wit's end. My poor niece has been waiting for this for 3 weeks while I've been working all this out.
EDITED: PS, I guess this means I still need the 10.0.2 updater if you know where I can get it.