Okay, here goes. I've searched the web and found references to the issue, but can't fix with the referenced documents.
Problem: All domains open the same "Default website for IP address" (henceforth called "Default website...") virtual server.
Operating system Debian Linux 7; Webmin version 1.680; Virtualmin version 4.06.gpl GPL; Theme version 8.7
Changing the "Default website..." in the Server Configuration -> Website Options changes the website that is displayed.
The access_log/error_log entries always show up on the "Default website..." files.
The access_log/error_log entries always show the domain name that was requested, not the "Default website..." domain.
So this seems like it means the FQDN is being passed to Apache correctly, and the Apache system is handing the "default website..." incorrectly, no?
So what am I missing? What do I need to configure or unconfigure?