I had similar error. I closed Flock (similar web browser than Firefox) when gnome-panel crashed, NetworkManager applet also crashed and apport alerted me.
-- [apport] gnome-panel crashed with SIGSEGV https://launchpad.net/bugs/82153 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
