I would very much like to know why it is that my working test client stopped working in the manner described in my earlier post in this thread. However, I think it very doubtful that SE will ever tell me or anyone else.

I have uninstalled the test server client, then downloaded all the files again and re-installed it. It is now working.

It may be that it would have started working again the next time they do an update to the test server client, but now I will never know. It had been working just fine until the update to the client that was made available on August 24. After that update, the FFXI Test Server client would not work on my system until I re-installed it.