Well, I'm assuming it was renaming the files via automator AFTER I'd imported them into iphoto that caused the problem. Since I had a backup, I probably should have just killed the whole library and copied the backup, as then I wouldn't have lost my editing work. But instead, I just reimported the photos and started over.
So -- word to the wise. DON"T use automator to rename something in iphoto AFTEr yoou've already imported them. iphoto doesn't like this.