When a 389DS directory (or RHDS) has been created in Crowd, creating a group via the Crowd interface results in an LDAP Error 21 - invalid value for an attribute.
CWD-180, Crowd now creates groups with a null member value, so the group can be created. However, it seems that some directory servers such as 389DS do not allow null values; and will throw LDAP Error 21.
To work around this, administrators must create the groups in LDAP first, and sync them back to Crowd so they can be populated as per normal.
It would be nice if Crowd (for directory types that required it) had the ability to add at least one real member to the group as it's created to avoid this message.