I don't know about the other browsers, but Chrome allows you to look inside and change some of the settings. The other problem seems to be the mac-forums not responding to some cookie etc. settings, and/or not updating some for some reason.
I finally got things working by going back to my original password that used to work, and changing some of the Chrome cookie settings as much as I could. Some seem to be encrypted so I left them alone.
I also tried using a little utility called Cookie.app which may have contributed to part of the solution, but I'm not a hundred percent sure. Regardless it has some very good user comments and reviews, especially for keeping one's browsing safe.
I ended up using their old 4.6 version to be compatible with Mavericks 10.9.
Cookie 5.9.10 free download for Mac | MacUpdate
Cookie 5 by SweetP Productions