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

• Don't make any changes on the Safe mode start window.

See:

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

Well the mystery is over. After restarting in Safe Mode I noticed that my tabs were at the top, and remembered seeing this as an option. I just restarted and when to turn that off and now everything is back to normal. I guess that my TabGroupManager add on is not meant to support this feature that I must have accidentally turned on.

Thanks for the help.