Issue with virtual hosts in Apache 2.2.9 on Debian

I've had a strange issue with my Apache instance on my Debian box since I
updated it earlier this week. I'm using Debian's stock configuration for
enabling name virtual hosts (even though I currently only have one site active).
In my ports.conf file I have this:

Listen 80
NameVirtualHost *:80

<IfModule mod_ssl.c>
    # SSL name based virtual hosts are not yet supported, therefore no
	 # NameVirtualHost statement here
	   Listen 443
</IfModule>

Then I have virtual host stanzas in /etc/apache2/sites-available/default like
this:

<VirtualHost *:80>
	[. . .]
</VirtualHost>

It seems like until earlier this week, that "Listen 80" line was unnecessary,
but when my default site no longer loaded, I added it in, and now everything's
fine. I've tried to read the Apache documentation for virtual hosts, and that
"NameVirtualHost *:80" clause looks like it's all I should theoretically need
for requests on port 80. When I comment the Listen 80 out and reload the
configuration, it doesn't listen anymore.

Anyboday have any ideas about what's going on?

Thanks.

Scott Denlinger