If your clients experience slow internet name resolution, or internet name resolution fails, while forwarding queries using DNS, but local intranet name resolution works, your DNS cache file is probably corrupt.

1. Stop the DNS service - net stop dns

2. Switch to the DNS directory - cd %SystemRoot%\System32\Dns

3. Rename the cache file - ren cache.dns cache.old

4. Copy the backup cache file - copy backup\cache.dns cache.dns

5. Start the DNS service - net start dns