Clarification: my problem was that I had not
been seeing the drop-down menu under "Quick Links" for some reason. Instead, when I would click on "Quick Links," I would see the links"mark forum read" link appear on the link bar itself. See here
In any case, the situation has been resolved. FWIW, I have been using FF (with NoScript) for some time and had not made any
changes to the EQ site, but for some reason just the past week or so the "mark as read" link wasn't working (as noted above). Well, I tried in Comodo Dragon (Chrome) and was
able to successfully mark messages as read, so I knew the problem was with FF. Apparently, one of the scripts NoScript had been blocking (googleapis.com) needed to be unblocked for the Quick Links to work properly and for me to be able to post a message to the board. I don't know why the problem came up, since, as noted, I made to changes whatsoever to NoScript.
Anyway, now everything is working as it should again. Sorry for the inconvience.