Hah! Well that made me chuckle! Coming from the approach that I want it to "just work", I think I'd rather have hemorrhoids than subject myself to any more testing than I've suffered already.
Workflow details: I'm working on a dual G5 PowerMac, using Leopard 10.5.8 and iMovie '09 to edit HDV footage from my Canon camera. From iMovie, I've been exporting to AIC 1440 x 1080, with PCM Big Endian sound at 16 bit, 48kHz. (I haven't nailed it down, but in general it seems more likely to make it thru an encode if I delete the sound track first. That's fine for my workflow, read on.) The movie file is dragged into the Toast window, with the Green background and the Blu-ray to DVD options selected. I've set the encoding to AVC at 15 average, 17 max, because I'm trying to max out the quality. It may be borderline but it does work in general. I click on "save as disk image" and, when it works, rescue the .264 file that shows up in the "Roxio Converted Items" folder. Don't quit before you move it!
Audio goes a different way. I drag the movie file into Soundtrack Pro and export the audio as a pair of mono .aif files, one for each channel. Oh, important step here, I make sure the audio timeline matches the video exactly in length. iMovie will actually export a shorter audio file when the move ends with a fade to silent background. In Toast, a short audio file will later be stretched to fit the video, and this causes havoc with sync. Been there, done that. Anyway, then I drag the L and R files into Compressor and let it prepare an .ac3 file surround mix. My "simple" mix is just duplicating the fronts to the surrounds, and letting Compressor make an LFE and center channel. I've also made a more complicated mix with music, which is what started this awful torture.
The video and audio are reunited by giving them the same name, eg. movie.264 and movie.ac3, and placing them in the same folder. Then when you drag the .264 into the Toast window (same settings exactly as before), it will find the audio file and mate it up. If it doesn't see it, it'll ask. Then when you hit "save to image" again, and all goes as hoped, it will skip re-encoding and go straight to multiplexing. No sweeter feeling than when it works!
My current project was one big movie and one smaller one. To isolate my problems, I ended up slicing the big piece into 3. So of the 4 total pieces, all 7-11 minutes now, 3 can be placed together on a disk image successfully using the process above. I'm struggling now with the 4th and final piece.
FWIW, I do see timing issues where Toast sees the .264 as being a different duration than the movie file it started as. That seems likely to cause problems but the file with the worst discrepancy is working fine. I've also suspected that titling errors caused by iMovie might be mucking things up. iMovie seems to have trouble exporting titles at HD resolution (dropping down a bit in res clears it up). My one remaining problem piece does contain some "fancy" moving titles. They look OK when previewed in Quicktime (unlike some others I've removed) but I'm wondering about them. Deleting them is probably the next thing to try if the current encode fails.
That's about all I can think of. It's a tough nut and I swear I've had success by simply re-trying a failed attempt. Hardly a solution. Oh, another wild idea: Is it possible a Toast encode can fail simply because it has taken so long? I mean, these things have sometimes gone two days just to quit unexpectedly at the end, but not before deleting the encoding .264 file. Could it be that the Mac's maintenance scripts are interfering, or the change in date is confusing Toast? Just grabbing at straws here, but it does see that the separate pieces are far more likely to succeed than one big file.