Ubuntu 7.04 with Ispconfig - The URL is not reachable!

[shellNewbie]

I have just successfully installed Ispconfig on Ubuntu Server 7.04 and everything went very well (watching Ispconfig install via Putty was as exciting as watching Die Hard 4!!). The only problem I had right at the end was when the ISPConfig install asked me for my Hostname and domain - I kept getting this error :

The URL is not reachable!

I left the Hostname blank and put the static IP of the machine into the Domain name and got to the end of the install which told me to browse to (mystaticip):81 and I wasn't able to do this. The domain was registered a few months ago with DynDNS.org so my question now is how to change my Domain name and Hostname to what they should be. I am new to both Linux and ISPConfig to any help is very much appreciated.