Well, as an update, I've been going back and forth with Vibeke to try to solve the problem, and we've made some progress. In case anyone else is experiencing a similar problem, here's what we've learned so far:
- The voice files for the CD and DVD versions of the game are compiled differently (I'm thinking it's so that they could span multiple CDs).
- Probably because of that, the script files for the CD and DVD versions of the game are compiled differently too and are incompatible with each other (using the CD exe on a DVD install or vice-versa will throw an error, even if unpatched).
- If you use the translation-patched DVD exe with the translated script files, it'll work but you'll get no voices. If you try to patch the CD exe the way the DVD was patched to read the script, the script comes out as "gibberish" (because the CD script is supposed to use a different offset).
So, the moral of the story (for those keeping score, or who can't follow all that technical jargon) is, for now at least, buy the DVD version of the game, because the CD version is not fully compatible with the current translation patch.