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

• http://kb.mozillazine.org/Clearing_the_cache
• http://kb.mozillazine.org/Cookies
• http://kb.mozillazine.org/Websites_report_cookies_are_disabled

You can try if it works in Private Browsing - Use Firefox without saving history mode. In PB mode the disk cache is not used and also a new set of cookies will be created.

Thanks....i had no luck, though.

As a troubleshooting matter, going to private browsing DID allow me to sign on to the troublesome sites.

HOWEVER, I clicked the clear cache button repeatedly to no effect. I also have FF set to automatically clear cache on exit; so i rebooted the browser. I had already deleted every cookie associated with these sites (like Yahoo mail)

And I just can't get it to accept a sign -in

Works fine in private browsing. Works fine from Chrome Works fine from IE Works fine from FF on my desktop Works fine with Facebook and some other sites

But I still can't get into these troublesome sites normally.

Update: I have meticulously cleared cookies/cache at least 5 times. I actually got to a point where it worked again. I thought everything was ok. The minute I rebooted the browser---back to square 1.

Something is going on that is interfering but I can't figure out what it is--or what to do about it.

One other odditiy---I noted the browser had some buttons of extension (ie. Morning COffee) suddenly disappear. I saw that extension was disabled--not something I did knowingly--and re-enabled and was able to replace the button, but it was odd it disappeared all by itself, along with some others.

Here's what SEEMS to have solved it. Before I came here I had cleared the cache and cookies to no effect. Perhaps I missed one. But that is a necessary part of the solution.

First, clear your cache and every cookie associated with Yahoo mail. (yahoo.com or www.yahoo.com) or other troublesome sites.

Second, I found that the next time I closed the browser, despite apparent success, I was back to square one. I had to again clear cache and get rid of the cookies. This is the really odd part.

I can't say I found an elegant solution at that point or why this was happening---but this time I simply refused to close the browser for awhile. And then suddenly everything was ok. Or seems to be. We'll see if the problem reoccurs. My theory is that continued use overwrote whatever was causing the problem.