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Title
Object reference not set to an instance of an object error when selecting a synchronization targets in GPOAdmin. -
Description
When selecting a synchronization targets in GPOAdmin the following error is seen: -
Cause
A replication conflict has occurred and a CNF object is created in the Default naming context in Active Directory partition. -
Resolution
Try steps from KB # 4225686 and KB # 4323092.
If you are not able to identify the conflict entry or entries (CNF or non-guid objects) with the steps from the above KB, then run the following LDAP query to identify conflict entries in all domains in which GPOADmin manage group policies:
1- Run LDP.exe
2- Click on Connection, then click on Bind.
3- Bind as current user or specify a different credentials and click ok.
4- Click on Browse, then click on Search.
5- Base DN: This should be the policies container in the domain where GPOADmin is installed. ex "CN=Policies,CN=System,DC=DOMAIN,DC=NAME"
6- Filter: (&(objectCategory=groupPolicyContainer)(!(displayName="[GPOADmin Working Copy]*"))(!(displayName="[QGPM Working Copy]*")))0
7- Scope should be set to OneLevel
8- Attributes: objectClass;name;cn;displayName;gPCWQLFilter
The above should look like the following:
Run the above query against all Domains in which GPOADmin manage group policies. There are two fields from each object which we use the GUID values from.
First CN. This should be a GUID with no other characters. A non-GUID returned here will give the same error seen in GPOADmin console.
The second will only exist on GPOs which have a WMI filter applied. The gPCWQLFilter should appear as the fqdn of the domain, then the guid, then an integer separated by commas. If the entry after the fqdn of the domain here is not a GUID this will also cause the parse error.
If the above query identifies the conflict object (CNF), then delete this CNF object and after that try to select a synchronization target to confirm that issue is no longer present.