1&1, popular website hosting service and domain name registrar, have a very serious problem with their nameserver configuration web interface.
We’re hosting our own domains with 1and1 (pointing to our dedicated servers hosted with the excellent and much-recommended Lunarpages), and were attempting to reconfigure our nameservers to point to a different IP address. We went into the 1&1 admin interface and attempted to re-configure the neosmart.net nameservers to point to the new IP – a week later, the DNS hadn’t yet propogated and we couldn’t find a good explanation.
This was how we had originally set up our nameserver entries in the 1and1 web administration center: