This was in my messages log. What does it mean please? Aug 7 14:20:38 ns named[710]: Lame server on 'elstreefilmstudios.co.uk' (in 'elstreefilmstudios.co.uk'?): [193.243.233.10].53 'ns0.cerbernet.co.uk'
That nameserver (ns0.cerbernet.co.uk) is listed as the second DNS server for the domain - the error was probably caused because when your server asked for a DNS record for that domain (elstreefilmstudios.co.uk) for which it did not have the information.
On checking when that server is asked about that domain it just returns that it is not authorative for that domain.
It has probably just been mis-configured or not-configured - i.e. not told that it is supposed to be the secondary nameserver or perhaps the IP address of the primary nameserver has been changes and again it (as secondary) has not been told.
Thanks...