After an eternity, I knew it was time to upgrade my OS. I did so about a week ago. This week, I went to use Soundtrack Pro. It opens, and seems to function normally, but when I click either save or export, the glorious rainbow deathwheel appears. I don't know that this is directly related to the upgrade, but that's the only thing I've done that I think could have affected it.
I'm thinking of pulling another upgrade, but with it not working at present, I'm doubtful that an upgrade could "fix" anything that a previous upgrade broke.