Aside from installing the add-on, are you able to connect Firefox to the internet ??

• Connection Settings

Yes I can connect to the internet and do so regularly. My primary problem is that the loading of a number of web-sites effective hangs with a "waiting for s7.addthis.com" message (or sometimes, waiting for something else). My hope is that I can use Addblock Plus to eliminate this problem.

Perform the suggestions mentioned in the following articles:

• Clear Cookies & Cache
• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

Check and tell if its working.

-> Also, Update All your Firefox Plugins -> https://www.mozilla.org/en-US/plugincheck/

• When Downloading Plugins Update setup files, Remove Checkmark from Downloading other Optional Softwares with your Plugins (e.g. Toolbars, McAfee, Google Chrome, etc.)

Thank you for your advice mha007. I cleared cookies & cache as per instructions. Another problem that I have had is that the Tools/Add-ons tab is only partially displayed and with no working hyperlinks. This is still a problem after clearing cookies & cache. I did previously get to the Add-ons page (from which I tried to download "Adblock plus") through another route, but I don't now recall how and have not been able to find my way back there. So I can't say if clearing cookies and cache solved the download problem.

I have also checked my plug-ins. There is 1 "Update now" - that is Shockwave flash. The download of the update file worked but the update itself failed. Adobe help advised me to run it's uninstaller, but attempts to run that have also failed. There are 3 "Update" and 8 "Research" plugins (just 2 are "Up to date"). I am new to plugins. I did some time ago spend some hours on a previous shockwave flash update, but have not otherwise had anything to do with plugins. It is 2:00 in the morning now: I will get back to plugins - but it may take some days - and I will report back.

Perform the instructions in the article -> Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems first before moving on to Updating your Plugins..

Thank you for your interest mha007. This is an update on my evenings activities so far.

I have done that trouble shooting with results, as follows: Started in safe mode In Tools/Options/Advanced/General, I unchecked "Use hardware acceleration when available" Clicked on Tools/Add-ons "Get add-ons" displayed "Loading" indefinitely All 5 Extensions are dis-abled: it suggested that I remove "Microsoft.net framework assistant 1.2.1" & "Test pilot 1.2". On "Microsoft.net framework assistant 1.2.1" I Clicked "Remove". It remained but with version 0.0.0. On "Test pilot 1.2" I clicked "Remove". It disappeared. The single Appearance "Default 9.0.1" is disabled None of the 16 plug-ins are disabled. I clicked on Add-ons and "Get add-ons" displayed "Loading" Several minutes later I found that, "Add-ons" had loaded. I clicked on "Most popular" and then on "Add to Firefox " within "Adblock plus" A pop-up box displayed "Add-on downloading", and "unknown time remaining - 0 bytes (0 bytes / sec)". Within a minute, a Firefox "Alert" pop-up window opened with the message: "An error occurred during a connection to www.mozilla.org:443 / The OCSP server experienced an internal error. / (Error code: sec_error_ocsp_server_error)" I bookmarked the "Most popular add-ons page" I closed Firefox and opened it again - not in safe mode. Clicked on Tools/Add-ons. "Get add-ons" displayed "Loading". In Extensions, on "Microsoft.net framework assistant 1.2.1" I Clicked Disable", and Restart Firefox I clicked on Tools/Add-ons. "Get add-ons" displayed "Loading". Message displayed "Connected to services.add-ons.mozilla.org. Waited. 10 minutes later I opened a new tab and clicked on the "Most popular add-ons page" bookmark. Message displayed "Connected to add-ons.mozilla.org". Waited. 15 minutes later, neither of the tabs had responded. I re-started firefox in safe mode I clicked on Tools/Add-ons. "Get add-ons" displayed "Loading". Message displayed "Connected to static-ssl-cdn.addons.mozill.net" Using the new tab from above which was not active on restart, I clicked on the "Most popular add-ons page" bookmark. The bookmarked page opened. I clicked on "Add to Firefox " within "Adblock plus" Again, a pop-up box displayed "Add-on downloading", and "unknown time remaining - 0 bytes (0 bytes / sec)". (No Alert this time).

I don't know what to read into all of this. Any advice on what the next best thing to do would be appreciated.

Sorry about the formatting of that big long paragraph. It was broken into readable chunks when I posted it. This is my first time using this forum, so I'm learning as I go.

Perform the suggestions mentioned in the following articles:

• Unable to install add-ons (extensions or themes)
• http://kb.mozillazine.org/Unable_to_install_themes_or_extensions_-_Firefox

Check and tell if its working.

In the "about.config" page, typing "xpinstall." resulted in the list being reduced to 5 entries. None of them have the "enabled" extension. All of them contain "whitelist" in the name. Typing "xpinstall.enabled" results in an empty list. Might this be the source of my problem?

There are sometimes connection problems with the server that hosts the add-ons (I'm currently seeing this) and in that case you can see the 0 bytes (0 bytes / sec) message staying instead of the download progression bar.

You need to try later another time to see if it starts working.

I made a few attempts to download a couple of weeks ago and another few attempts today, all to no avail. I will continue trying to download and to implement any suggestions I receive e.g. from mha007.

Create a New Profile

• Basic Troubleshooting - Make a New Profile

Using the new Profile, check if you are able to install AdBlock Plus or some other add-ons.

Check and tell if its working.

Created a new profile; left the old profile as was.

Opened Firefox under the new profile. Could not load Add-ons page: neither through Tools/Add-ons nor my bookmark to Most popular add-ons.

Opened Firefox under the new profile in safe mode. Could not load Add-ons page: neither through Tools/Add-ons nor my bookmark to Most popular add-ons. Yesterday, in safe mode, the bookmarked page opened - not today.

Apart from the specific add-on that you are trying to install, are you unable to install any other add-ons ??

One of my problems is that I can only get to the Add-ons page intermittantly, and not at all through the Tools/Add-ons route. Today, I can't get to the Add-ons page at all, so I can't try to install any Add-on now,

• Go to the site - https://addons.mozilla.org/en-US/firefox/
• Install any add-on (for testing)

Check and tell if you are able to install an add-on.

I've tried the suggested link. I just get a "Connecting" tab title with the message "Connected to add-ons.mozilla.org" on the bottom of the screen. This is the site that I have bookmarked and that sometimes opens and sometimes not.

Use other browsers to go to this link. Check if its opening easily on other browsers.

I quit Firefox and opened Internet explorer (the only other browser I have installed). I tried the link. The tab title had something like "Firefox add-ons", the progress bar showed some mevement but there was no traffic on my local area connection and nothing loaded.

Can you tell any other websites on which you are having the same problems ??