Today on my Ubuntu 10.04 machine I received the following error: “Firefox is already running, but is not responding”. I tried this article to clear my profile: http://kb.mozillazine.org/Browser_will_not_start_up, but it didn’t work. I tried: “killall firefox-bin” and it didn’t work either. I even tried starting firefox with a new profile by: “firefox -p”, but it couldn’t start. What I had to do was:

Note: This will clear out plugins/addons/settings/etc. For me it was acceptable because I was locked out.

1. Go into Synaptic Package Manager
2. Do a Complete Removal of Firefox
3. After it’s complete
4. Go to a terminal and:
   • cd ~/.mozilla
   • rm * -R
5. This cleared out all the profiles, etc.
6. Then do a re-install in the Synaptic Package Manager

That was my fix and I hope that helps someone out there. Sucky fix.