hello Malachor, could you provide a screenshot that shows the issue - maybe this makes it easier to understand what might be going on...

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

Do a malware check with some malware scanning programs on the Windows computer.
Please scan with all programs because each program detects different malware.
All these programs have free versions.

Make sure that you update each program to get the latest version of their databases before doing a scan.

• Malwarebytes' Anti-Malware:
  http://www.malwarebytes.org/mbam.php
• AdwCleaner:
  http://www.bleepingcomputer.com/download/adwcleaner/
  http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender: Home Page:
  http://www.microsoft.com/windows/products/winfamily/defender/default.mspx
• Spybot Search & Destroy:
  http://www.safer-networking.org/en/index.html
• Kasperky Free Security Scan:
  http://www.kaspersky.com/security-scan

You can also do a check for a rootkit infection with TDSSKiller.

• Anti-rootkit utility TDSSKiller:
  http://support.kaspersky.com/5350?el=88446

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

If you can't download the scanners on that computer then use another computer and save them to an USB jump drive.
Make sure to download and save the latest virus signatures.

Thank you for your responses. I appreciate it.

@ Cor-el: Thank you for your suggestions but as I have already explained in the initial post, I have already tried everything you mentioned.

Here is the screenshot:

http://s28.postimg.org/4jy3tm78t/screenshot.jpg

thanks - does the dialog always refer to ajax.googleapis.com or to multiple different websites?

Did you try to boot the computer in Safe Mode?

You can also try to reset (power off/on) the router.

See also:

• http://kb.mozillazine.org/Error_loading_websites

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

Hello,

Thanks again for the quick responses. I appreciate your time, effort and suggestions :)

I will do as you suggest Cor-el and provide an update later today.

@ Philipp: Yes, it's always from that URL. Very strange.

Thanks again

Mal.

I have seen that type of message before. The site (usually a pay site) requires that you log in first. Have you been on those sites in the past? Has this happened before?

Hi,

Thanks for your response :)

The issue occurs on multiple sites (completely at random so I can't list specific ones - apologies); even sites I've visited before with no issues, which is why it's such a headache for me as I've no idea what has changed to make this happen. As an aside, I can confirm no changes to my router/firewall have been made in over 6 months, yet this issue only surfaced about 3-4 weeks ago.

From now on, when you get that message, STOP. Open a new window. This will give you someplace to work. Open the History folder and check the last few entries. Now go back to the passworded page. If you can, Firefox toolbar > Tools > Page Info > General. Take a snap shot and post it here. Do not use the Firefox add-on if you have it. Use Windows Start > in the search-bar enter > Snipping Tool. We only need to see the window with the Page Info.

Thank you for your suggestion :)

The issue disappeared yesterday for whatever reason, yet has re-surfaced right now, on the exact same sites that worked yesterday. The only thing I have done (that has changed) is run a full sweep of CC Cleaner (with Cc Extender Options all enabled) and wiped the free space on all my drives.

Also, as for your instructions, I'm afraid I do not have a "tools" option anywhere; just the standard orange "Firefox" button in the top left of the screen which gives me the choice for Bookmarks, History, Downloads, Addons, Options, Help etc. I replicated the error, opened up a new Window and attempted to get the 'page info' under 'general' but simply couldn't find any option/button with the label. I right clicked all over the page hoping it might of been a hidden feature but nada unfortunately.

The snippet tool via Windows Search worked fine however.

I apologise if I'm doing something wrong.

Not sure if this is pertinent but this is what CC Cleaner (with extender) wipes with regards to Firefox:

http://s2.postimg.org/4qmsi64wp/CC_Options.png

It is always best to avoid using such external cleaners as you can never be sure if they aren't corrupting files and it is usually not worth the trouble to repair damage if that is the case. A lot of the SQLite database files use a complicated table setup that can easily get corrupted.