Create Computer Groups in AD

We have recently extended our AD schema with the extensions sent to us by our Apple SE. We used the provided batch file to import the new schema. We are able to edit the MCX settings for any existing user, group and computer account. Just like it is supposed to work. The problem we have is, how do we create computer groups? We cannot create a computer group through Workgroup Manager, we receive the following error. How can we create computer groups and manage the MCX settings through Workgroup Manager? eDSNoStdMappingAvailable error -14140