You have a lot of installed extensions, so a first thing you can try is to check Toshiba websites with Firefox Safe mode: add-ons will be temporarily disabled.

To start Firefox in Safe Mode, close Firefox and start it again while holding down the shift key.

You can check the connection settings.

• Tools > Options > Advanced > Network : Connection > Settings
• https://support.mozilla.org/kb/Options+window+-+Advanced+panel

If you do not need to use a proxy to connect to internet then try to select "No Proxy" if "Use the system proxy settings" or one of the others do not work properly.

See "Firefox connection settings":

• https://support.mozilla.org/kb/Firefox+cannot+load+websites+but+other+programs+can

Do a malware check with several malware scanning programs on the Windows computer.

• https://support.mozilla.org/kb/troubleshoot-firefox-issues-caused-malware

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:
  http://windows.microsoft.com/en-us/windows/using-defender
• 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

I found the problem and fix for my case.

Problem

The Toshiba home page was still closing the connection with no text and no explanation today.

But a product page I reached through web search provided a plain diagnostic text (identifying numbers changed to 0):

this page is being redirected and logged. Please contact application support: Transaction ID = 0000000-PPE2 Session ID = hxsL85/KAa2ixV3PmpOZUNIzzL4A020 Violation Category = APPFW_SIGNATURE_MATCH Violation Log = 000.000.000.000 0000000-PPE2 hxsL85/KAa2ixV3PmpOZUNIzzL4A020 toshibab2c-profile http://www.toshiba.com/us/computers/laptops/satellite/radius14 Signature violation rule ID 14989: web-misc novell edirectory soap accept language header overflow attempt <blocked> Session Cookie : -

I put the clue in bold above: the site found something amiss in the accept-language header.

Investigation

I went to menu / options / content ( about:preferences#content ) and clicked Languages [Choose ...]

It showed:

 English [en]
 English/United States [en-us]
 [chrome://global/locale/intl.properties]

The last line (which I put in bold above) is not a language.

Before I removed it, in about:config I searched for intl.properties and found:

 extensions.qls.backup_acceptlanguages;chrome://global/locale/intl.properties
 intl.accept_languages;en,en-us,chrome://global/locale/intl.properties

Speculation

The last line in the languages dialog is longer than a language code like en or en-us, and it looks like a URL, so that may be why the site thought it was suspicious and rejected the page request.

Maybe the 'intl.accept_languages' option was corrupted by the 'qls' extension. (I don't think I have such an extension installed now, but it may have been corrupted many years ago. Maybe Quick Locale Switcher? I don't remember if I ever installed it, but it is possible.) Or maybe the 'intl.accept_languages' option was corrupted by an update function that combined the entries with the words 'acceptlanguage'.

Fix

In the content Languages dialog ( about:preferences#content ) After I removed the erroneous language, the Toshiba site worked again.

I hope this helps.