Linux server - my domain name takes me to my router setup!

[#1]

I've setup a server using Ubuntu 7.04 Feisty Fawn Linux and registered a domain name.  When I access the domain from another PC e.g. my work evrything works fine.  When I try the same from within my own network my domain takes me to my router setup page.
This is also causing me problems setting up a mail server as my client program can't find my domain - my suspicions are is to do with the above.  Being going round in circle on line trying to find a solution but getting lost.
Help!!

[#2]

For many routers, it's not possible to access them via their external address from inside your network, whether using your domain name, or the WAN IP address, you get the exact effect you are seeing now, you get the setup pages.
I'm not certain how to get round this for Feisty, or any flavour of Linux to be honest, but for windows, I would put an entry into the hosts file for each machine on the network, that redirects your domain name internally, to the LAN IP address of the PC running the server software.

[#3]

I guess you are using the external IP address on an internal networked PC. This will not work with most routers as they will get confused, and in your case your router thinks you want to access itself.
Internally you need to use the internal IP address so just add the domain name to your windows or Unix hosts file and use the internal IP address.
The other option is to setup your own DNS on the Linux or a Windows box and change all internal PCs to use it which can then resolve the domain to the internal address.

[#4]

Many thanks guys.  I added the name to the hosts and added an alias.  Working fine now.