It is possible that your security software (firewall, anti-virus) blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program.

Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full, unrestricted, access to internet for Firefox and the plugin-container process and the updater process.

See:

• https://support.mozilla.org/kb/Server+not+found
• https://support.mozilla.org/kb/Firewalls

• https://support.mozilla.org/kb/fix-problems-connecting-websites-after-updating

Thank you for your advice. I have reloaded Mozilla on the Windows firewall list as per sugested procedure. It did not change the situation. I have temporarely Disabled AVG. That made no difference.I then tried to remove FF. That requested me to close FF. This was not possible for no FF window shows. Windows taskmanger also did not show it as running so no avail there. I have closed and started and removed Mozilla. Remains Mozilla Maintenance Service. I cannot remove that; I have not sufficient access. It needs the syatem Administrator. I have two PC'S on a network and a external harddrive for backup. Who could possibly be the System Administrator?

Hello,

Certain Firefox problems can be solved by performing a Clean reinstall. This means you remove Firefox program files and then reinstall Firefox. Please follow these steps:

Note: You might want to print these steps or view them in another browser.

1. Download the latest Desktop version of Firefox from http://www.mozilla.org and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu).
3. Delete the Firefox installation folder, which is located in one of these locations, by default:
   • Windows:
     • C:\Program Files\Mozilla Firefox
     • C:\Program Files (x86)\Mozilla Firefox
   • Mac: Delete Firefox from the Applications folder.
   • Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory.
4. Now, go ahead and reinstall Firefox:
   1. Double-click the downloaded installation file and go through the steps of the installation wizard.
   2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

More information about reinstalling Firefox can be found here.

WARNING: Do not run Firefox's uninstaller or use a third party remover as part of this process, because that could permanently delete your Firefox data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. These cannot be recovered unless they have been backed up to an external device!

Please report back to see if this helped you!

Thank you.

Many thanks for your interest! I have followed your recommended path to the letter. I now have FF icon. FF does page does not show when double clicked. Apparently FF is open for when trying to remove it I am instructed to close FF first. The task manager does not show FF as running so I can not close FF there.(see above) Closing is not possible other than closing down and restart.

Sometimes when FF is closing, not all of it shuts down properly. On Windows, start the Task Manager (Other systems may have different names). Select Applications (list of what user programs are running). If you see Firefox listed, try to shut it down normally. If it does not shut down, then on the Task Manager right click FF, and select End Task. However, if FF still does not shut down, or FF is not listed as running; on the Task Manager, select Processes. Look down the list for Firefox. Right click and select End Task. If this problem keeps coming up, ask for more help.

I might not have stated clearly what does or does not happen. I run XP on a PC..FF is installed and when icon double clicked to open nothing happens. Taskmanager: nothing shows in Applications nor Processes. On controlpanel: remove: cannot remove Close FF first. on :/C; Programfiles cannot delete FF Access denied. Restart .Then open program files and delete FF and Mozilla Service manager

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) as a test to see if that helps.

I do not know if this is the root of the problem: Opening in Safe Mode does not work: NTLDR is missing. To fix this I have to go back to the installation disk. As I bought the thing preinstalled I will have to go back to the supplier or is there another way to get NTLDR fixed. Does this now start to look like a better startegy to upgrade to windows 8?

NTLDR is a critical Windows file and something either erased it or malware deleted it somehow.

Anywho, if you have the Windows installation CD, you can just insert the XP CD and when it is done loading, press R to go to the Windows Recovery Console.

There, you can restore the critical missing file. Type these one by one: Replace [cddriveletter] and [OSdrive] with your respective drive letters.

copy [cddriveletter]:\i386\ntldr [OSdrive]:\
ex:
copy D:\i386\ntldr C:\

copy [cddriveletter]:\i386\ntdetect.com [OSdrive]:\
ex:
copy D:\i386\ntdetect.com C:\

Go to Microsoft.com and start a search for what you need.

Well,thanks to all who have made my plight theirs. I have downloaded Revo Uninstaller( free ware) and thoroughly removed all traces of FF. Then reinstalled and it works again.

So the original problem is solved. I am working on my NTLDR file buit that will sort itself out. Thanks to all!
Maas