What's wrong? - Something to do with lead.

I think this does what you want:
Code:
select ue, cod_id,
CASE WHEN max_rtype = min_rtype THEN max_rtype ELSE 'N/A' END rtype,
area
from
(select ue, cod_id, area,
 max(decode(r_type,'N/A',null,r_type)) over (partition by ue, cod_id) max_rtype,
 min(decode(r_type,'N/A',null,r_type)) over (partition by ue, cod_id) min_rtype
 from  TAB_TEST2)