Two weeks later, and I FINALLY found out what was causing the log-in issues: The virus program BitDefender. It has worked fine for years (it was one of the most highly recommended free virus programs), but two weeks ago, something must have happened with it that prevented me from logging into FSM (and Dropbox too, it turns out). I have now uninstalled the software, and can log in on my laptop again! Hooray! I have lots of threads to catch up on now.
Ha, ha...thanks. But I'm willfully ignoring most of that (I see it's prevalent in the DUNE threads), and just forward my positive reactions instead (plus, I have Totoro/Andre Lux on my ignore list, so I'm not even opening that thread of his).