Your Windows Server 2003 Directory Service event log contains entries similar to:
Event Type: Error Event Source: NTDS Replication Event Category: Internal Processing Event ID: 1481 Description: Internal error: The operation on the object failed. Additional Data Error value: 5 000020D9: SvcErr: string varies, problem 5001 (BUSY), data Event Type: Error Event Source: NTDS Replication Event Category: Replication Event ID: 1084 Description: Internal event: Active Directory could not update the following object with changes received from the following source domain controller. This is because an error occurred during the application of the changes to Active Directory on the domain controller. Object: object DN Object GUID: ef688125-9639-4238-88db-68b663844609 Source domain controller: guid-based DC name Synchronization of the local domain controller with the source domain controller is blocked until this update problem is corrected. This operation will be tried again at the next scheduled replication. User Action Restart the local domain controller if this condition appears to be related to low system resources (for example, low physical or virtual memory). Additional Data Error value: 8409 A database error has occurred.This behavior occurs when an Active Directory object that is currently being used is deleted from the Active Directory directory service.
NOTE: The replication engine will attempt to move the object to the Deleted Objects container later.