When you attempt to establish a VPN connection to a VPN server, you receive:
Encryption failed because no valid certificate was found.
This can occur on a new connection or on one that previously worked.
The error is produced because the connection is incomplete. You should:
1. Verify basic network connectivity between the client and the server.
2. Make sure that you have name resolution between the client and the server.
3. Use the Networking and TCP/IP troubleshooter in the Windows 2000 Help.