Windows has a tendency to cache negative DNS lookups so that even if you fix a DNS problem you still cannot look up a name. A negative DNS lookup occurs when trying to resolve the address for a name that has no corresponding DNS record.  There is a registry entry that specifies cache times for DNS.  One of them specifies how long to cache these negative entries.  I would suggest setting it to zero so it will always try to query a DNS server even though the name did not exist before.  Doing this might save you some confusion when troubleshooting DNS issues.  Read about it here

There is also a dnscmd Windows Support tool that is handy for updating DNS without having to run the GUI.  You can read about it here