We changed the IP addresses of NS3 and NS4 to:
NS3 => 126.96.36.199
NS4 => 188.8.131.52
The new servers again in Sofia, Bulgaria. They have different connectivity and promote maximum productivity ClouDNS platform.
Old servers will be up to 01.01.2011
If you are Premium customer and use the service DNS Branding is necessary to change Glue records for your domain with new ones.
If you have free account, you don't need from any changes. This is only good news for you, your name servers are better from now.