Thanks Victoria. FWIW, this isn't a big deal, just annoying. As suggested, I selected all cookies from the lightroom queen webpages, there were about 10 or so, and deleted them. I then went back to the forum via my link to Recent Posts. I was asked to log in, which I did manually putting in both username and password, even though Firefox had filled in them automatically. I was then properly logged in. I'll let you know what happens over the next few days.
~3h later: I had closed Firefox, ran some errands, and then came back to the computer. I clicked my Recent Posts link and was prompted to login, ie., the site did not retain that I had clicked the stay logged in box. Firefox had filled in my username and pw, so it was simply a matter of one additional click and I was logged in and reading the recent posts.