Separate Issue; Your System Details shows;

Installed Plug-ins

Shockwave Flash 16.0 r0 Shockwave Flash 19.0 r0 Shockwave Flash 14.0 r0 Shockwave Flash 20.0 r0
Having more than one version of a program may cause issues. You must remove the older programs. Then get the current full installer.

Flash: Grab the uninstaller from here: Uninstall Flash Player | Windows Uninstall Flash Player | Mac

Then reinstall the latest version.

Flash Player Version 20.0.0.235
https://www.adobe.com/products/flashplayer/distribution3.html Note: Windows users should download the ‘’’active_x’’’ for “Internet Explorer,” and the ‘’’plugin’’’ for “Plugin-based browsers” (like Firefox).

Note: Windows 8 and Windows 10 have built in flash players and Adobe will cause a conflict.

Adobe still offers Flash 18.0.0.268 as its extended support release further down

Enter about:config into your Firefox address bar Click the I'll be careful button Find xpinstall.signatures.required in the list Right click the preference Select Toggle until the value is false

OK thanks FredMcD, I uninstalled the lot as you told me, then pulled down & installed Shockwave Flash 20.0 r0, AND 14.0 r0 was back there too. So I clicked on the "Update Now" for 14.0 r0, dowmloaded & installed the result & still have both versions there. I have already been to about:config and done that, but Firefox still blocks Adobe Acrobat DC - Create PDF, Dashlane and WordWeb one click lookup because of "Add-on signing in Firefox" Every time I update Firefox I have to go in addons & reset Flash player to "Always Activate" because default appears to be "Never Activate", but the others, even with the about:config work around do not work.

Type about:plugins<enter> in the address bar. Now search for the plugin.

Example; Adobe Acrobat File: nppdf32.dll,nppdf32.dll Path: C:\Program Files (x86)\Adobe\Reader 11.0\Reader\browser\nppdf32.dll,C:\Program Files (x86)\Adobe\Reader 11.0\Reader\AIR\nppdf32.dll Version: 11.0.9.29 State: Enabled Adobe PDF Plug-In For Firefox and Netscape 11.0.9

This will show you the path to that program. Copy the Path Only. Also note the name of the file, and remember it. Now Close Firefox. Open your file browser and paste the path in the address bar. Find the file, and delete it. Now you can restart Firefox. Warning ! Remember to delete the right program.

To be safe, remove all of them. Then install the current.

Thank you again FredMcD. I have marked it 'Problem "Solved" because I have solved the problem very easily. I have decided to cease jumping through hoops for whoever is now in charge of ruining a once excellent browser & have chosen to install Google Chrome. It is not as 'user friendly' as Firefox, but it does allow me to have the addons & plugins I want.

... from the frying pan and into the fire.

You think Google Chrome is better? It lacks the depth of extensibility that Firefox has had forever. When you install Chrome in installs an "updater" program that runs whenever the PC is running, which Google uses to keep Chrome (and other Google applications) updated automatically whether any of those application is being used or not at the time the update is downloaded. I don't trust one company enough to allow them to "know" what I search for thru their search engine and use their web browser for, and then "agree" to allow them to have access the my PC via a process that is running whenever my PC is turned on.

And now that the US Government / US Congress is talking about forcing companies like Google, Apple, and others to have a "back door" to their applications for the government to use - what would stop the NSA from looking inside a Google users computer remotely? "They" can already intercept our internet traffic, listen to our cellular phone calls, and read our email - why not just install a Google application (or "let" Google install another hidden application thay you may not even know about) that might make it possible in the future for the NSA to crawl right into your PC?

Yes, "big brother" relies upon humans to be ruled by emotion rather that logic; sheep to be led to slaughter. So please, give him what he wants by using Google Chrome; less chance "they" will have the time to try to get data from people who use logic for decisions.

Thank you for your reply the-edmeister, No, I do not think Google Chrome is better, I do not particularly like Google Chrome, but I do like it better than Internet Explorer. I did use Firefox for a long time, and I used to like it. It was fast, it was user friendly. But now it has changed. I have noticed with each new update that it has become slower & slower to load. In fact just recently I have been opening Firefox to my home page (Firefox) & the whole browser stops dead & the top bar informs me "Firefox has stopped responding", so I wait, & eventually it will start again. I have put up with this for a few months, but now it has decided to disable my addons. So the whole thing has come to a head & I no longer use Firefox. Perhaps I will give it another look in the future, if it gets rid of the bloat, & if it stops treating me like a child it has to protect from itself.

IMO, the biggest cause of Firefox slowing down over time is issues with the Firefox Profile. "A Profile doesn't last forever" is one of my favorite mantra's with regards to Firefox.

Back in the old days when Firefox received a new major updated version once a year (or year and a half), I would create a new Profile every other new version (like every 1 1/2 or 2 years). Now since the advent of the Rapid Release schedule (starting with Firefox 5.0) I recommend doing a new Profile when there's been an accumulation of changes that in the olden days would have constituted a "major" version. Firefox 29 was one of those "events" in and of itself. And Firefox 40 / 43 is another. But its' not an exact "science" and lot depends on how many and /or which extensions the user has installed (and /or may have "tried out" and then removed). Over time a lot of "chaff" can accumulate in the Profile and will slow down Firefox, and might cause other minor issues. A new Profile can work wonders for "restoring" Firefox performance, but it can be time consuming and requires a fairly thorough knowledge (or the reading of a KB page to "walk you thru it") of all the files that are in the Profile folder, which in time can change as new files are added with new features, or files are replaced by a "better way of doing things".

A year or so ago Firefox received a Reset / Refresh button to give the user a "fresh start", which basically creates a new Profile while saving the important user data that accumulates thru use of Firefox. https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings See the - What does the refresh feature do? section to learn more about it.

Currently, I am very unhappy with the recent changes in Firefox (specifically, add-on signing and the "new" Search Bar), and if I do switch to a different browser it sure as hell wouldn't be Chrome which has a much "tighter rein" on what the user can do, than Firefox has. My choice ("without naming names") would definitely be another Gecko-based browser. http://geckoisgecko.org/

Thank you again the-edmeister, Well I reinstalled Firefox, & it hasn't frozen on me ... so far. But it still will not allow me to use my addons, Dashlane in particular, which fills in my login details, I set up an account, I put in MY password, and it is not acceptable. It is too short, it has to have uppercase, it has to have lower case, it has to have numbers, it has to have symbols, it can not include my birthdate, or my phone number and a month down the track I have to change it for security reasons.????? How in hades can I remember passwords without dashlane, so I have to use IE or Chrome, because they understand & allow Dashlane. Wordweb allows me to highlight a word & check its meaning, or if I type the word, check its spelling. How is this dangerous for me, or for Firefox? Acrobat DC addon allows me to convert a web page to PDF, that does not frighten me, but it appears it scares Firefox. None of the three addons are now allowed, but they were in the past. What has changed? What is Firefox afraid of?

I have no idea which "account" you are talking about, but reported issues with Dashlane in Firefox go further back than the release of Firefox 43, as I recall - like maybe as far back as Firefox 40 or 41. But just in case Dashlane fixed their recent past incompatibility problem, maybe the issue now is "signing" in Firefox 43. Although Dashlane should have known about "signing" back in Firefox 40 if not a lot earlier and taken care of it when / if they fixed something a little while ago.

See this support article > Add-on signing in Firefox Specifically this paragraph - What can I do if Firefox disables an installed, unsigned add-on?

There's an add-on - https://addons.mozilla.org/fr/firefox/addon/install-unsigned-add-ons/ - to "automate" this procedure.

Override add-on signing (advanced users): manual method You can override this setting by changing the xpinstall.signatures.required preference to false in the Firefox Configuration Editor (about:config typed in the URL bar). Support is not available for any changes made with the Configuration Editor so please do this at your own risk.

Note: That pref will be gone in Firefox 44 (Release slated for Jan 26. 2016) so user's of currently un-signed extensions should contact the developers of those extensions and prod them into getting their act together & get their extensions signed by Mozilla. Otherwise the users of those extensions will be SOL come the release of Firefox 44. Mozilla has already pushed back the version in which this new security feature was to be enabled from Firefox 40 to 44. I doubt if there will be any further reprieve.

"My Account" - I was generalising, it is not Firefox, it is accounts for various websites that require a user name & password to login. Every so often they require that I change my password for my own good, & they stipulate what my password should be , in as much as it now has to have a mixture of upper case, lower case, numerals & symbols. Actually it does apply to Firefox as I need to sign in here to answer you, but as of yet they have not suggested it is time to change my password)

https://addons.mozilla.org/fr/firefox/addon/install-unsigned-add-ons/  takes me to a page, in French, where, as far as I remember my French from school some 50 years ago, says they are sorry but they can not find the page.

I have only recently, say a month, had Dashlane installed, & it worked then. It is only just before Christmas (22/12/15) that it stopped working, and it appears from all the replies I now have to 'jump through hoops' to try to fix it. I have already been in to about:config & changed it to false, & the three addons I have been talking about still do not work. Why does Firefox have addons if they do not let them work?

the-edmeister said

There's an add-on - https://addons.mozilla.org/fr/firefox/addon/install-unsigned-add-ons/ - to "automate" this procedure.

This link is no good. All I found was this;

Untrusted Add-on Switcher https://addons.mozilla.org/en-US/firefox/addon/untrusted-add-on-switcher/

Yeah, it looks like that extension was pulled from AMO. I knew it was available in the 23rd or the 24th when I put that link to my Clippings file. Sorry, I guess I should have checked that link today when I posted ot here.

Information about the pref is provided here, which I hyperlinked above: https://support.mozilla.org/en-US/kb/add-on-signing-in-firefox

"Why does Firefox have addons if they do not let them work?"

Signing is a new anti-malware move by Mozilla to prevent add-ons fro messing with users settings / preferences, and some times locking prefs making it hard for the user to reset the changed preference. The Add-ons Blog announced all the way back in Feb 2015 that the feature was going to be added Firefox. And a "warning" message about "not verified" was added in Firefox 40. So who knows what the add-on developers were thinking when the ignored the information that was provided?

OK. Thank you both FredMcD and the-edmeister.

I have now worked out how to keep Firefox & keep my addons working. I have installed Firefox 42.0b9 where everything works, after a fashion, And I have disabled automatic updates until such time as this madness ceases & Firefox again allows its users to run the addons they want to.

I am still advised that "Adobe Acrobat DC - Create PDF could not be verified for use in Firefox. Proceed with caution", and the same for WordWeb one click lookup. I am prepared to accept responsibility & proceed with caution, and I have the addons I want to use. Which is how it should be.