Hi stylesjack, Are you launched in safe mode? It is also possible to temporarily disable extensions and themes to see if this is not an issue.

It is also possible to check to see if there is a lock file in the profile folder, but I do not think that is it.

Does this also happen with a clean reinstall?

You can use one of these to start Firefox in Safe Mode:

• On Windows, hold down the Shift key while starting Firefox with a double-click on the Firefox desktop shortcut
• On Mac, hold down the Options key while starting Firefox
• Help > Restart with Add-ons Disabled

• https://support.mozilla.org/kb/Safe+Mode

I had the same problem. Found out that it was because I enabled multiprocess e10 in Nightly.

What I did to fix it was go to the General tab in Nightly and disable e10.

Hope this helps