The following KB has recently been published http://support.microsoft.com/kb/951380 and a hotfix is available.
When you run a discovery operation in Microsoft System Center Operations Manager 2007 Service Pack 1, and a cluster node is discovered, some computer properties may not be collected for the cluster node. For example, the DNS host name, the security identifier (SID) and the Active Directory organizational unit of the cluster node may not be collected. Therefore, some Operations Manager workflows may not function correctly. For example, if the DNS host name is not collected in an Operations Manager 2007 environment that has the Microsoft Exchange Server 2007 Management Pack applied, the following event may be logged:
Event Type: Warning Event Source: Health Service Modules Event Category: None Event ID: 10720 Date: Date Time: Time User: N/A Computer: ComputerName Description: The Backwards Compatibility mapper module was not able to start because discovery has not fully completed for this Health Service. This is a transient issue, the affected rule(s) will be unloaded and the Health Service will restart them when initialization is complete.
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