It has been already from nearly two years ago, that under certain circumstances DNS Server service on Windows Server 2008 R2 refuse to resolve internet domain name addresses.
This issue occurs if Windows Server 2008 R2 DNS Server is used without forwarders configured, just relying on root hints entries querying for internet domain name resolution.
The issue was, that after a while the DNS Server service can’t handle the catched entries on the DNS cache and refuse name resolution.
Now Microsoft published a hotfix to fix this issue, which was still persistent on Windows Server 2008 R2 with Service Pack 1.
Get the hotfix here: