[apache] Apache error: _default_ virtualhost overlap on port 443

To resolve the issue on a Debian/Ubuntu system modify the /etc/apache2/ports.conf settings file by adding NameVirtualHost *:443 to it. My ports.conf is the following at the moment:

# /etc/apache/ports.conf
# If you just change the port or add more ports here, you will likely also
# have to change the VirtualHost statement in
# /etc/apache2/sites-enabled/000-default
# This is also true if you have upgraded from before 2.2.9-3 (i.e. from
# Debian etch). See /usr/share/doc/apache2.2-common/NEWS.Debian.gz and
# README.Debian.gz

NameVirtualHost *:80
Listen 80

<IfModule mod_ssl.c>
    # If you add NameVirtualHost *:443 here, you will also have to change
    # the VirtualHost statement in /etc/apache2/sites-available/default-ssl
    # to <VirtualHost *:443>
    # Server Name Indication for SSL named virtual hosts is currently not
    # supported by MSIE on Windows XP.

    NameVirtualHost *:443

    Listen 443
</IfModule>

<IfModule mod_gnutls.c>
    NameVirtualHost *:443
    Listen 443
</IfModule>

Furthermore ensure that 'sites-available/default-ssl' is not enabled, type a2dissite default-ssl to disable the site. While you're at it type a2dissite by itself to get a list and see if there is any other site settings that you have enabled that might be mapping onto port 443.