66: Operation not allowed on non-leaf (4239179)

After running a directory sync the below information is seen in the log file.

Obsoleting Structure : 10/23/2012 4:01:37 PM
Delete Structure | ou=cmn,o=quest
LDAP Return | 66: Operation not allowed on non-leaf

This occurs when the Coexistence Manager for Notes tries to delete the OU called CMN when there was no objects to sync but the CMN OU has existing entries from another directory connector and therefore not able to delete this CMN OU.