The agent operation failed on %ServerName; because DPM could not communicate with the DPM protection agent. The computer ...

The agent operation failed on %ServerName; because DPM could not communicate with the DPM protection agent. The computer may be protected by another DPM server, or the protection agent may have been uninstalled on the protected computer.
If %ServerName; is a workgroup server, the password for the DPM user account could have been changed or may have expired.