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 http://support.microsoft.com/kb/318803.
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 http://technet2.microsoft.com/WindowsServer/en/library/5c497b2e-3387-4ecf-adf5-562045620a961033.mspx.