I have this same problem but mine seems to be even worse: I can't manage to open *any* https link in FF even if it's already started and if I copy&paste the URL from another app. (and I get that screen with the "Check to make sure your system has the Personal Security Manager installed" etc etc).
I can workaround this only using Mozilla Web Browser. I'm using FF package 1.99+2.0b2+dfsg-1ubuntu2 -- Opening firefox by clicking on links in thunderbird breaks https https://launchpad.net/bugs/57923 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
