Mirror Domain Not Working



I am developing a new version of a site so have setup a server for it.

Given it is a live site somewhere else I then setup a mirror site using murdermostfoul.dreamhosters.com

All was well for about an hour. I installed Wordpress and a few plugins but then suddenly I get the message, “Server not found”

The main server is www.murdermostfoul.co.uk but as I say I cannot access it other than by a Mirrored site, as per the Dreamhost Wiki I read.

Can you help?