Today struggling with Debian server upgrade and come across this:
Starting web server: apache2 [Thu Jan 31 18:25:41 2013] [crit] (22)Invalid argument: alloc_listener: failed to get a socket for (null) Syntax error on line 9 of /etc/apache2/ports.conf: Listen setup failed Action 'start' failed. The Apache error log may have more information.
Long story short - had to upgrade Linux kernel. Thanks to Major Hayden for his post where he is mentioning this.