ping cannot find host but nslookup on a host works just fine:  

Ping request could not find host HOST. Please check the name and try again.

Restart the DNS Client Service in Windows Services to resolve this one.  A few other commands to try:  

• ipconfig /flushdns
• ipconfig /registerdns

Following this, check eventviewer why it stopped working, to begin with.  The service is started using:

C:\Windows\system32\svchost.exe -k NetworkService

Alternately, stopping the caching daemon (DNS Client) in Services also works.  Also check Event Viewer -> Custom Events -> Administrative Events for any failures.  After doing the above, disable and reenable the network interface.  

Additional commands to try:

• route /f
• netsh winsock reset catalog
• netsh int ip reset reset.log

After all this, the issue was resolved on our side.  Alternatively, reconnect to the network if originally connected via WiFi.

Cheers,
Tom K