try this:
select os.ea_guid AS CLASSGUID, os.Object_Type AS CLASSTYPE, os.Name as SourceObject, os.ea_guid as SourceGUID,
c.Connector_Type as ConnectorType, ot.Name as TargetName, ot.ea_guid as targetGUID, count(*)
from ((t_connector c
inner join t_object os on os.Object_ID = c.Start_Object_ID)
inner join t_object ot on ot.Object_ID = c.End_Object_ID)
group by os.ea_guid , os.Object_Type , os.Name , os.ea_guid , c.Connector_Type , ot.Name , ot.ea_guid
having count(*) > 1
order by count(*) desc
Geert