Thanks for responding, Peter. Unfortunately, your suggestion does not solve the current mystery, because all the staves are set to display lyrics.
The problem i described occurs right there inside the LYRIC WINDOW. One moment, the lyrics are present. As soon as
<ctrl> <click assignment> is invoked, the lyrics immediately disappear from the LYRIC WINDOW.
There was actually a previous post describing this same bug, but none of the responses to that query ever solved the problem. Could this possibly be a systemic Finale bug? I sure hope not. I never encountered it until just now.
Like Peter, I have not seen this problem, and I use Windows for my day-to-day music work. Have you submitted this to the "Submit a request" link at the top of the page, where you can include a sample file for MM Support to analyze?