Comment # 12 on bug 1192978 from Carlos Robinson

Restarted FF via Alt-F2 prompt instead (then entering "firefox -P Small
--no-remote --safe-mode"), and I still can not open links from Thunderbird. I
get:

Firefox is already running, but is not responding. To use Firefox, you must
first close the existing Firefox process, restart your device, or use a
different profile.


The fact that disabling all add-ons one by one does not affect the tabs not
working behavior, but safe mode does, maybe indicates that it is not an addon,
but a theme the culprit.