this morning, i get alert from DPM server like below:
The following alert occurred at 6/13/2010 12:21:01 AM.
Description: Backup to tape failed.
DPM failed to communicate with BJ-MBX-66.xxxx.xxx because of a communication
error with the protection agent.
For more information, open DPM Administrator Console and review the alert
details in the Monitoring task area.
One DPM agent can not be connected.
after research, find this is due to the windows firewall settings missing.
and now worked.
this is a common issue after install the windows patch. So if you find same issue, first check firewall settings.