This issue can be caused by the McAfee Site Advisor extension

• https://support.mozilla.com/kb/Troubleshooting+extensions+and+themes

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.com/kb/Safe+Mode

Disable "McAfee Site Advisor" extension which was just updated to 3.4.0, which probably took it out of the addons block list.

• "Ctrl+Shift+A" > find McAfee Site Advisor and use "Disable", and then restart Firefox.
• Do a Google Search no problem
• It seems that if you re-enable Site Advisor again, and restart Firefox you are okay. At least you know where to look if you get the error again or Google searches slow down.

This was almost the solution, but you left out a few steps:

1) Open Firefox 2) Select the Tools menu 3) Press CTRL+Shift+A (or simply select the Add-Ons item from the Tools menu) 4) Choose Extensions 5) Disable McAfee Site Advisor 6) Close Firefox 7) Restart Firefox

Also, if I re-enable McAfee Site Advisor the problem recurs.