Start Firefox in Safe Mode {web Link} by holding down the <Shift (Mac Options) > key, and then starting Firefox.

In the address bar, type about:crashes<enter>. Note: If any reports do not have BP in front of the numbers, click it and select Submit.

Using your mouse, mark the most resent 7 - 10 crash reports, and copy them. Now go to the reply box below and paste them in.

If you can't get Firefox to open, you will have to do this the hard way. Open the file browser / explorer on your computer. Enter this;

%APPDATA%\Mozilla\Firefox\Crash Reports\submitted

Copy the last 5-7 Recent File Names in the folder, including the date and time created. Post all the information in the reply box below.

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