The problem could be the double-click speed of your mouse. If you're running Windows, you can change this setting in the Control Panel.

If you're noticing double-click behavior when you only single-click in other applications as well, you may need to replace your mouse. I bought the mouse that I am currently using to replace one I had that was causing this same problem.

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

There are other things that need attention.

Your System Details List shows multiple Flash plugins.

• Shockwave Flash 15.0 r0
• Shockwave Flash 16.0 r0
• Shockwave Flash 17.0 r0

You can find the installation path of all plugins on the about:plugins page.

• http://kb.mozillazine.org/Issues_related_to_plugins#Identifying_installed_plugins

You can check the Flash player installation folder for multiple Flash player plugins and remove older version(s) of the plugin (NPSWF32) and possibly (re)install the latest Flash player.

• (32 bit Windows) C:\Windows\System32\Macromed\Flash\
• (64 bit Windows) C:\Windows\SysWOW64\Macromed\Flash\