You said a couple of your sites bring up the test page. Does that mean your are using virtual hosts?. If you have more than one site and only one public ip, you'll need to use name based addressing. All sites will need to have their own vhost container, including your "main" site. The server in the main section will not work anymore. If it is still serving the index from the DocumentRoot defined in the "main" section, then the virtual hosts are not setup correctly. Here are a few thing to check:
ServerName localhost #Set to localhost, machine name or commented out
Listen 192.168.1.20:80 #Will listen only for this address on port 80
UseCanonicalName Off #Set this to Off
NameVirtualHost * #Use name based addressing
<VirtualHost *>
ServerName mydomain.com #Each vhost MUST have this
ServerAlias
DocumentRoot "/path/to/index.html/" # You MUST also have this
Your directives and directory containers also go here
</VirtualHost>
I think somebody already wrote an FAQ on how to setup virtual hosting so you may want to take a peak there for more info.