Nothing will open in a new tab.
Normally, when you click a link, it opens in the current tab. If you want to open a link in a new tab instead, just right-click on the link and select Open Link in New Tab from the context menu. This option no longer works since I upgraded to the current version of firefox. Nothing will open in a new tab.
I disabled my addons and went one by one restoring them to look for an interfering addon. But when I did this Firefox worked fine and the "Open in New Tab" function worked as well as links designed to open in a new tab rather than the current window worked.
But, shortly after that the problem reappeared. I did the disable addons and reapplied them one by one. I ran CCleaner and Glary's Utilities and Spybot Search & Destroy and my anti-virus scanner (Comodo Anti-Virus & Firewall)