• "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"

When I had this problem, I went to Tools->Options->Privacy. Then click "Use custom settings for history", then change third-party cookies to "Keep until they expire" (make sure "Accept cookies from sites" is checked). That fixed it.

igrb.roo, that may work, but people choose not to give up control of preventing third party cookies for good reason. We should not be forced to accept all such cookies just to be able to avoid the harassment of that screen.

I never got this message until FF was automatically upgraded to 13.0. I only see it happen when I'm logged into my Yahoo home page. After awhile, my browser window starts to display a different home page along with the message, "We noticed you may have signed in or signed out in another window. Click OK to reload your page." and I have to acknowledge the popup to redisplay my Yahoo! home page.

i suppose you've already tried the suggestions above. not sure if it might be related, but in recent days there have been reports of leaked passwords of users from major sites like linkedin, eharmony & lastfm. in case you've used any of these services and happen to use the same password for your yahoo-account, please change your password immediately since it might be used to break into your account...

please also scan your pc for malware: Troubleshoot Firefox issues caused by malware

I did try the above suggestions, but they didn't help. I just reverted to FF 12.0 and the problem has not reoccurred.

Try to reset Firefox.

• https://support.mozilla.org/kb/reset-firefox-easily-fix-most-problems

As bsilverstein noted, this only began with version 13.0 and it only occurs on my.yahoo.com.

Removing peoples option to reject third party cookies is not an acceptable solution. I hope Mozilla corrects the glitch.

Confirming also that this problem just started for me with the new Firefox 13.0 and the my.yahoo.com page.

Unable to load My Yahoo homepage without getting popup : "We noticed you may have signed in or signed out in another window. Click OK to reload your page."Started with FF13.. Will have to revert to FF12 as there appears to be no solution to this annoyance.

Reverting to FF12 did resolve this annoyance. Unfortunately, I left the automatic update option enabled and now I'm at FF14, with the same annoying message. I'm going to change my update setting and once again revert to FF12.

Firefox will only update to Firefox 14 if you you are on the beta update channel (Help > About), so make sure that you install the Firefox 12 release version if you really want to downgrade to that version (not recommended).

• http://releases.mozilla.org/pub/mozilla.org/firefox/releases/12.0/win32/

I know firefox needs a permenate fix but Thankyou for suggesting to reset the browser. It works great!!!!!!

Problem still persists with Firefox 13.0.1 ... reverting back to 12.0 for now

Where can we download FF 12?

Download older versions of Firefox here

<strike>http://www.oldapps.com/firefox.php</strike>

<Please only link to the Mozilla servers to download Fire - edited by moderator>