Name Server Unreachable - one or more name servers for this domain can not be reached. Please contact the admin for the name server:
Somebody can explain me what is happening here? I changed the name servers, but after that, they do not work! why??? is this a hosting problem? or a domain problem?
Usually this is caused when the webhost does not add an entry in their name server config file for your domain. Please contact your webhost and ask them to add your domain to their webserver.