Can't look at this now as I'm away from home and not back 'til Friday.
The "fiddling" was merely to expose the downloads. However, other parts of the web config are acting up so that's likely the issue. I'll raise it with Haven.
Actually, fairly simple answer. The downloads from the server for PAM and other mods are actually done through Promethius' web server. Behind the scenes a web server upgrade had happened and some stuff broke during that. Those problems are (largely) rectified but it took realising there was a problem to get to fixing them.