After just following the steps above, visiting enum.cn shows the "This Connection is Untrusted" dialogue for me on Windows.  According to the bug report here: <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=173729" rel="nofollow">https://bugzilla.mozilla.org/show_bug.cgi?id=173729</a> I believe the steps above are all you should need to do.