The source material is five video clips all in Apple ProRes 422 LT format and I have Toast 12.1 set to encode at 26.0 Mbps with Dolby Digital audio at 320kbps (same settings I've used a hundred times before). To add insult to injury, last night I FINALLY got it to successfully finish encoding a project, which it then saved to a disc image (.toast) file... and then of course crashed just as it finished writing the disc image file! Needless to say, when I burned that disc image to BD-R it has errors and freezes up about 3/4 of the way through. So back to the drawing board I go now. Great.
I do still have my older Toast 10.0.9 installed, so I think I'll either use it today or try using Time Machine to revert back to Toast 12.0.1. Both of those were stable in my experience.