Thank you for the prompt responses, folks. Yes, I was just coming back to post that I found a solution using the Google search engine.
I do have a suggestion for the MC 28 developers, though...If there was ever a time when a confirmation would be required, it would be when changing the language that the interface operates with. In other words, one should definitely receive a warning
and a "YES" or "NO" option relative to any language change. Initially, I changed the language from English to [something] with one inadvertent touch of my Mac trackpad, and was able to switch back to English the same way. I'm very happy to be back to my native language, but this shouldn't be possible via one touch of the trackpad. By the way, this suggestion is meant to be constructive.
Regardless, if anyone is using JRiver MC 28 for Mac and run into this language change issue, here's what I did to recover the English interface...
(1) From the main (top of screen) menu, select the 5th option from the left (Tools) ... NOTE: Disregard the bold "Media Center XX" label when counting during this process;
(2) Select the 2nd option -- from the bottom -- of the drop-down menu (Language);
(3) Select the 6th option -- from the top -- of the language list menu ... NOTE: the word "ENGLISH" should appear in this list.
This was a bit scary for a while, so I hope that this post helps other MC 28 for Mac [trackpad] users who drag their fingers like I do.