Question for you network/DNS/Apache gurus;

["John W. Foster" <jfoster81747@gmail.com>]

I have a web site established on a remote hosted VPS server system. 
I have full root access.
I use Debian linux on my personal system (wheezy) & on the remotely
hosted site (squeeze).
I use Godaddy as my domain registrar. 
I have the domain for the remotely hosted VPS site set up at Godaddy.
I have the exact IP address set up there to forward to the VPS site with
masking.
I have a tarball based mediawiki set up on the VPS site in /var/www/
There are no links in /var/www/ to the site, the opening page is
index.php & is in this directory.
I simply use the "/sites-enabled/default" in apache2 to send web queries
to the VPS site.

Up to here all seems to work OK.
Here is the issue.
When I try to access the mediawiki for configuration, using 
http://my.mediawiki.net (example)  the site will not work as it should.
It opens the startup page but will do nothing else.
When I access the site with http:// 123.123.123.123 (example numerical
IP address) the VPS site allows the mediawiki to run the configuration &
setup as it should.

This is my first attempt to manage a remote site so I really need
advice.
Any Tips are appreciated & BTW I did ask these questions on the
Mediawiki site, but alas no help there.
john