I have been doing som checking and noticed that the DNS servers for the domain were not setup correctly.

I have added the 3rd name server, but it will take a while for the DNS records to update.

I believe the problem to be caused by a record pointing to ns3, when ns3 was not listed as a name server for the domain.

For info:

CheckDNS.NET is verifying if NS are alive
NS list mismatch: registration authority reports that domain is hosted on the following servers: 'ns2.livedns.co.uk; ns1.livedns.co.uk', but DNS server ns1.livedns.co.uk reports domain to be hosted on 'ns1.livedns.co.uk; ns2.livedns.co.uk; ns3.livedns.co.uk'. Please make sure that you configure the same DNS servers in registrar database and on your DNS