Hi Marco,
I'm having exactly the same problem using the large data editor.
Bellow you will find the string I'm trying to put on a varchar2(4000) field using large data editor and that triggers the ORA-01480: trailing null missing from STR bind value:
BEGIN pk_prov_ndb_interface.get_service_info; pk_client_service.treat_create_client_service(service_name_i => pk_prov_ndb_interface.l_service_info.service_name, servicetypeid_i => pk_prov_ndb_interface.l_service_info.servicetypeid, service_relativename_i => pk_prov_ndb_interface.l_service_info.service_relativename, service_tectype_i => pk_prov_ndb_interface.l_service_info.service_tectype, service_bandwidth_i => pk_prov_ndb_interface.f_parse_string('BANDWIDTH'), subscriber_name_i => pk_prov_ndb_interface.f_parse_string('CLIENT_NAME'), nif_i => pk_prov_ndb_interface.f_parse_string('NIF'), subscribertypeid_i => pk_prov_ndb_interface.l_service_info.subscribertypeid, subscriber_node_i => pk_prov_ndb_interface.f_parse_string('CLIENT_NODE'), provisionid_i => pk_prov_ndb_interface.l_service_info.provisionid, service_exists_flag_i => 'N', errorcode_o => :errorcode, output_o =>

utput); IF :errorcode = 1 THEN :errorcode := NULL;

utput := NULL; pk_vadx.ps_vadb_bripots_aloc_port(i_tiporua => NULL, i_morada_rua => NULL, i_morada_num_pol => NULL, i_morada_andar => NULL, i_fraccao => NULL, i_localidade => NULL, i_edificio => NULL, i_edif_preinfra => NULL, i_sigle_pap => pk_prov_ndb_interface.f_parse_string('CENTRAL_ACRONYM'), i_cod_postal => NULL, i_contacto_tecn => NULL, i_telefone => NULL, i_fax => NULL, i_area_central => pk_prov_ndb_interface.f_parse_string('CENTRAL_AREA'), i_cod_site_dim => pk_prov_ndb_interface.f_parse_string('CLIENT_NODE'), i_agregado => pk_prov_ndb_interface.f_parse_string('SERVICE_AGGREGATOR'), i_class_debito => pk_prov_ndb_interface.f_parse_string('BANDWIDTH'), o_output =>

utput, o_errorcode => :errorcode); END IF; END;
If I try to update the same string via an update statement everything works OK.