So I started Vassal using your instructions to do it from a command terminal. I opened a new game from the module manager, and I was able to start a log file and save the game without a crash! Next I tried starting Vassal from the desktop. Again everything worked normally. I restarted the computer, started Vassal from the desktop and had no problems starting a logfile or saving a game. The only other change I had made was to clear out some space on my OneDrive. However all Vassal files should now be stored locally.
So I’m a little baffled on what actually fixed the problem, but very happy to apparently have it solved. I’m sure it was a Microsoft/Windows issue of some kind.
Thanks so much for the help, and the patience to explain things.