This article may help you to fix crashes.

Thanks Raiyad. I'd already tried that but with no success. I've realised now that Firefox only crashes when I bring up Google or youtube. Any other suggestions??

Do a malware check with several 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:
  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
• https://support.mozilla.org/kb/troubleshoot-firefox-issues-caused-malware

From your other post in the old thread about crashes on Google:

bp-07436670-fa4f-48b3-811c-f4a4e2150414 14.4.2015 20:12
bp-f648ee0b-dfe6-41bc-b66b-542b82150414 14.4.2015 16:47
bp-038e0ae5-c408-414f-8126-891fa2150414 14.4.2015 15:35
bp-cd8f9625-c76a-4288-ad45-3e57b2150414 14.4.2015 15:29
bp-3c7626f3-0dca-4245-8ae1-aee2f2150414 14.4.2015 14:39

Some unknown DLLs, possibly randomly named, appear to be crashing Firefox in those reports. If you haven't checked for malware per the above suggestion from cor-el, this would be a great time to do that.

https://support.mozilla.org/questions/1057380#answer-718076