All this started with the latest Firefox? Try downloading and old version, v24 maybe, and see if the problem is still there.

https://www.mozilla.org

Also could you please provide the link you used to download the latest version?

it persists for all the newly downloaded files. The one i could install was a set up file which i had saved to my hard disc at a time when that one was the latest version

https://www.mozilla.org/en-US/firefox/all/

this was the link i downloaded the latest version. I also tried filehippo

Most possible ways to update firefox are told in the Update Firefox to the latest release article.

I have tried that update method too. It says update failed :(

Have you tried an older version as I suggested? Have you been having any problems with your internet or modem? Check your firewall settings. We are all trying to help, but until we find the real problem, the only thing we can do is try a lot of ideas.

Don't try any older versions.

I've got two methods you can try, use ninite to try to install Firefox, http://ninite.com/firefox/

Or, download and install it from http://mozilla.mirrors.tds.net/pub/mozilla.org/firefox/releases/latest/win32/en-US/Firefox%20Setup%2025.0.1.exe

If you get an error message please put the exact error message and what point in the install you got it in this thread.

Thank you all for the support. It's solved. :)

this link you offered says: "can't find page" Ninite, as it started "run", then got an error: An error occurred. The certificate authority is invalid or incorrect [0x80072f0d] ; ; 216 any other ideas ? Any chance other browsers don't let me download Mozilla ? had if for years, went to update it, then uninstalled it, now neither Google Chrome or Internet Explorer will let me download it. Or maybe it is just my laptop, running on Windows 7 ? ? ? ? ? ?

mmeieio, are you accessing the site from a mobile device? http://williamfaulkner.co.uk/2007/06/windows-mobile-ssl-0x80072f0d-invali...Please consider creating a new thread containing the specific details of your issue.

Please, feel free to post the link to your thread on this thread for volunteers interested in assisting you.

Thank you.

@guigs2 No, not from a mobile device. Accessing the site from my laptop via wi-fi. FYI, I was able to download & install an earlier version of Mozilla FF, after repeated warnings that the "certificate authority is invalid". As I had rec'd the same warnings - I was using both IE & GC browsers - in my many attempts to download & install the latest version, I finally tried to D & L Mozilla FF v.26. I continued to get <<< [JavaScript Application] ! initXpcom Type Error. CompClass is undefined >>>> popped up one after the other; X'd them out over and over. Finally switched back to other browser (IE & GC) in order to view emails from Mozilla support (like yours). Then I gave up. However, after I had re-started my PC, that error did not come back, and I am able to use this older version (26) without difficulty. Wondering if I will be getting pop-ups saying I need to "update to the most recent version of Mozilla" - 28 ? Thank you for your input !