"Clear the Cache": Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now" "Remove the Cookies" from sites that cause problems: Tools > Options > Privacy > Cookies: "Show Cookies"

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of your add-ons is causing your problem (switch to the DEFAULT theme: Tools > Add-ons > Themes). See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

If it does work in Safe-mode then disable all your extensions and then try to find which is causing it by enabling one at a time until the problem reappears. You can use "Disable all add-ons" on the Safe mode start window to disable all extensions. You have to close and restart Firefox after each change via "File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit")

Thanks for your very quick response to my post. I have cleared cashes, cookies and history in the past and it takes a lot of time and eliminates items I want to keep as well as disturbing my other browsers. Since Firefox created the problem somehow in its update, I think I should not have to go through all that rigamarole to fix it. I was about to post that I would not follow your suggestion and would just use Safari until FF fixed the problem, when I tried FF once again and -- the problem was gone. I have no idea why. I really like FF and I am glad to have it back working for me as I like. This is the best solution, no action needed from me!!