You can also try starting Firefox in "troubleshooting mode": https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-modeThat will temporarily disable any extensions and some custom settings.Hope this helps!
I noticed the same problem in the same time frame. I managed to trace it down to an unexpected source: the "ClearURLs" extension. More specifically, when I disabled ClearURLs' option to "prevent tracking injection over history API", Google Voice star...
