Got it fixed.
So, I get to work this morning, sorting through everything, and suddenly have a cold doubt flash through my mind. And, upon getting home, I realized I was right. I forgot to update the English and Japanese folders before uploading 1.5.9.
I knew I was too tired to be staying up so long yesterday.
Anyway, I've updated the downloads for 1.5.9 with all the necessary text, which was the real cause behind the 'nofile' error. I've attached a quick patch to this post if you want to skip redownloading the whole thing, though.
Hopefully, that'll be all for major bugs now until I get the DLC compatibility done.