I cant see my active directory tree

When I double click on Active Directory I get this error message:

“Naming information cannot be located because:
The network path was not found. Contact your system administrator to verify that your domain is properly configured and is currentlyonline.”

The problem suddenly appeared and I cant access the active directory. I havent made any changes to the server’s TCP/IP settings.

When I run NETDIAG i get this message:

DNS test…: Failed
[WARNING] Cannot find a primary autoritative DNS server for the name “server1.myserver.com” [RCODE_SERVER_FAILURE]

How to fix this problem? Thank you.