This error is logged when a configuration file has been downloaded by a management server or agent and some further validation checks are being carried out.
For this particular error, it is checking the DnsNameOrIp property for the Child Health Services is correctly populated.
To help identify the invalid HealthService entry, run the following SQL.
USE
OperationsManager
SELECT * FROM MT_Computer WHERE NetworkName = ''
If this does not help identify a machine with an empty string for its computer name then you will need to capture a copy of the bad configuration file which you can do with the following steps on a second managment server which is reporting the same issue. To do this use the following method
On your second Management Server, stop the healthservice/System Center Management service.
Rename the Health Service State folder to Health Service State.old.
Then restart the service, watching the OpsMgr event log until you see an event like this
Log Name: Operations Manager
Source: OpsMgr Connector
Date: 04/02/2011 08:38:37
Event ID: 21023
Task Category: None
Level: Information
Computer: <ServerName>
Description:
OpsMgr has no configuration for management group <ManagementGroupName>and is requesting new configuration from the Configuration Service.
Then stop the healthservice once more on this management server.
If you time this well, the configuration file for the management server will be left in the \System Center Operations Manager 2007\Health Service State\Upload Files directory on the Root Management Server after a few seconds/minutes, and that should have the detail you need.
Collect the configuration file, which will be a numbered file without a file extension and open it in an XML editor and examine the Child section for any anomolies.
Resolution
Once you have identified the rogue agent from the configuration file or SQL query above, remove this agent from the managment group and wait for the data to groom out (+48 hours) before reinstallation.