After installing the DNS role in Windows Server 2008 any queries made against the server are not resolved.
Chances are that you are running Windows Server 2008, if this is the case Microsoft released a fix to correct such issue, you can download it here:
You will need to provide your email address to download the executable, once you extract it, simply install the update and reboot your server.
Your DNS server should now be able to resolve unknown addresses using the root hints servers.
You can easily use nslookup command to test it such as:
cmd: nslookup google.com localhost