Maybe i was not very clear, but the same configuration worked up to 0.8.3 included, upgrading to 0.8.4 fail due to bind issue, downgrading to 0.8.3 works fine with no change in configuration.

As usual apache2 listen on port 80
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
apache2 11963 www-data 4u IPv6 1976954 TCP *:www (LISTEN)
apache2 11964 www-data 4u IPv6 1976954 TCP *:www (LISTEN)
apache2 11965 www-data 4u IPv6 1976954 TCP *:www (LISTEN)
apache2 18919 root 4u IPv6 1976954 TCP *:www (LISTEN)
apache2 27514 www-data 4u IPv6 1976954 TCP *:www (LISTEN)
apache2 27515 www-data 4u IPv6 1976954 TCP *:www (LISTEN)
apache2 27520 www-data 4u IPv6 1976954 TCP *:www (LISTEN)
apache2 27521 www-data 4u IPv6 1976954 TCP *:www (LISTEN)
apache2 27523 www-data 4u IPv6 1976954 TCP *:www (LISTEN)
apache2 27524 www-data 4u IPv6 1976954 TCP *:www (LISTEN)
apache2 27596 www-data 4u IPv6 1976954 TCP *:www (LISTEN)
apache2 31555 www-data 4u IPv6 1976954 TCP *:www (LISTEN)
apache2 32109 www-data 4u IPv6 1976954 TCP *:www (LISTEN)

And nginx listen on port 8080 (at least when running 0.8.3)

The real issue is that the 0.8.4 is trying to bind on port 80 while the conf files are telling it to bind to port 8080. The configuration files have not changed for months, it's the first time i encounter the issue.