Prueba haciendo una subconsulta.
algo mas o menos asi:
Código SQL
[-]
SELECT D.KOD, A.Descl, SUM(CantCred),SUM(CantCont)
FROM
(
Select D.KOD, A.Descl,
(Case when C.TipoConsumo = 'K' then Sum (D.Cant) else 0 end) As CantCred,
(Case when C.TipoConsumo = 'C' then Sum (D.Cant) else 0 end) As CantCont
From tblconsumod d
left join tblconsumoc c on d.tdc+d.doc = c.tdc + c.doc
Left Join tblArticulo a on D.kod = A.KOD
where c.f_doc = '17/06/2011' and c.TipoConsumo in ('K','C')
group by D.KOD, A.Descl, C.TipoConsumo
) CONSULTA
GROUP BY D.KOD, A.Descl
Order by D.KOD