I used to get that as well, best to speak to live support and they will sort it straight away.
I think it is the named or host file (or one of those many files that i have no clue as to what they do) that needs editing to correct the error.
A record is missing for your Hostname which needs to be added on the dns server from where your domain name resolves. You can communicate with our team and ask them to fix this problem.