The thing is, just as OldTimeRadio has experienced, I download things from the Vault regularly, without this issue. I did so less than two weeks ago, in fact. I first noticed the issue clicking a link to a Vault file, then the same issue directly from the Vault page. I've used Firefox on the Vault many times without issue. It seems, from those traits, to be something new at least for me. Of course, something could have changed on my end, but even so it's something new.
I emailed Maximus the moment I realized it was happening, using the Vault's email. He hasn't responded.
Actually, the right-click, save as technique wasn't working for me either. However, today it is. *eyebrow*