I am using Firefox 54.0.1 on a Windows 10 platform. I use the same settings Nigel listed: accept cookies, 3rd party never, keep until expire, clear history on close (except cookies). Just for grins I changed it back to "keep until close" (which is the setting I used for years) and added an exception for Avast. That seems to have done the trick. It also eliminated those miserable capchas on this forum. Eddy, Nigel, thank you for the help and suggestions!