I don’t know if this is an issue with Firefox (3.0.10), Ubuntu (9.04), Apache2 or the default apache config file, but when trying to surf to a SSL-encrypted page on a default installation of Apache on Ubuntu, with a default self-signed certificate, Firefox (also a completely default installation, this is on a new system with nothing on it yet) just gave me a sec_error_ca_cert_invalid popup, without any possibility to add an exception. The “Or you can add an exception…” link I’m used to simply did not appear. Surfing into the site from a windows computer worked nicely.
After a (long) while I realized that whatever the problem was, it only appeared when surfing to https://localhost/ . If i surfed to https://computername/ , I got the expected behavior.
Weird.