Dropa – thanks for your reply. It was a pop up from Mozilla suggesting trying a “Test pilot program for Total Cookie Protection” which I accepted. All the problems started after that. Today I went into Privacy & Security settings and unchecked the option for “Test pilot…”. Computer seems to be back to normal now. After I unchecked the Test Pilot option, it no longer appears in the menu as an option, which I find interesting. It sounded like a great concept but my computer definitely did not like it. I attached an image of the menu before I unchecked it.

This offer for extra cookie protection is probably about new Enhanced Tracking Protection features.

• https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop
• https://support.mozilla.org/en-US/kb/smartblock-enhanced-tracking-protection
• https://support.mozilla.org/en-US/kb/trackers-and-scripts-firefox-blocks-enhanced-track