Apparently answering the door in the middle of replying to a forum post is punishable by having your message thrown away in your absence... Sorry for not typing fast enough, everybody! (edit: the actual crime appears to be leaving the thread open for too long in your browser, it doesn't matter if you type or not)

Rant aside, thank you @bwldrd. I think the problem is that I'm trying to install on Windows 7; the Vue X 1.8 User Guide says that Windows 8 is the minimum, but then goes on to describe what happens on Windows 7. I thought it was worth a shot, at least.

Since my post I've tried installing Vue X 1.9 (aka 2024) which failed immediately, and a fresh download of 1.8 (aka 2023) in case the first one was corrupted; I got the same error.

I couldn't find ecosystem_physics.vll on the path stated in the log, so it should be no surprise that the installer couldn't create a symlink to it; but according to my searches I appear to be the only person on the whole Internet to experience this problem, which wasn't the kind of notoriety I was hoping for. ;) Hey ho, no Vue for me.