thunderbird security exception is not permanently stored

Binary package hint: thunderbird

I have an IMAP server with a TLS cert signed by cacert.org, but thunderbird does not know about this CA by default, so it comes up with a dialog box asking me to add a security exception. I check the checkbox "Permanently store this exception", and click the "Confirm Security Exception" button. Immediately after confirming the exception, I am presented with the dialog box again. I have done this cycle atleast 15 times already. There is no time for me to interact with the rest of the GUI between "confirming" the exception and being presented with the dialog again. I have tried not checking the checkbox in case of inverted logic, but that doesn't solve the problem either.

Package: thunderbird
State: installed
Automatically installed: yes
Version: 3.0.4+nobinonly-0ubuntu1
Priority: optional
Section: mail
Maintainer: Ubuntu Mozilla Team <email address hidden>
Uncompressed Size: 33.8M
Depends: fontconfig, psmisc, debianutils (>= 1.16), libasound2 (> 1.0.22), libatk1.0-0 (>= 1.29.3), libc6 (>= 2.11), libcairo2 (>= 1.6.0), libdbus-1-3 (>= 1.0.2),
         libdbus-glib-1-2 (>= 0.78), libfontconfig1 (>= 2.8.0), libfreetype6 (>= 2.2.1), libgcc1 (>= 1:4.2.1), libglib2.0-0 (>= 2.23.5), libgtk2.0-0 (>= 2.18.0),
         libhunspell-1.2-0 (>= 1.2.8), libjpeg62, libnspr4-0d (>= 4.7.3-0ubuntu1~), libnss3-1d (>= 3.12.6), libpango1.0-0 (>= 1.14.0), libstartup-notification0 (>=
         0.10), libstdc++6 (>= 4.1.1), libx11-6 (>= 0), libxrender1, libxt6, zlib1g (>= 1:1.1.4)
Recommends: myspell-en-us | hunspell-dictionary | myspell-dictionary
Suggests: thunderbird-gnome-support (= 3.0.4+nobinonly-0ubuntu1), latex-xft-fonts, libthai0
Conflicts: mozilla-thunderbird
Replaces: mozilla-thunderbird
Provides: mail-reader
Description: mail/news client with RSS and integrated spam filter support
 Thunderbird is a lightweight mail/news/RSS client, based on the Mozilla suite. It supports different mail accounts (POP, IMAP, Gmail), has an integrated learning Spam
 filter, and offers easy organization of mails with tagging and virtual folders. Also, more features can be added by installing extensions.