Firstly, check to see which add-ons are installed onto your Firefox and uninstall/disable any add-ons that you do not remember installing or that you believe may be causing the issue.

If the issue is not related to an add-on, sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try these free programs to scan for malware, which work with your existing antivirus software:

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• Anti-Rootkit Utility - TDSSKiller
• AdwCleaner (for more info, see this alternate AdwCleaner download page)
• Hitman Pro
• ESET Online Scanner

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista if you don't already have one. Windows 8/10 have antivirus protection built-in.

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

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Separate Issue; Your System Details shows;

Installed Plug-ins

Shockwave Flash 21.0 r0 Shockwave Flash 23.0 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.

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. Install the plugin only. Not the active_x.

Flash Player Version: 23.0.0.162 Flash Player (Linux) Version 11.2.202.635

https://get.adobe.com/flashplayer/ Direct link scans current system and browser Note: Other software is offered in the download.

https://get.adobe.com/flashplayer/otherversions/ Step 1: Select Operating System Step 2: Select A Version (Firefox, Win IE . . . .) Note: Other software is offered in the download.