problems with foreign keys

[unreal4u]

hi everybody .. first post ... hope someone answers it ...

Well .. this is my problem ... I got 2 tables:

/*==============================================================*/
/* Table: TIPO_EMPLEADO                                         */
/*==============================================================*/
CREATE TABLE tipo_empleado
(
  id_tipo_usuario serial NOT NULL,
  nombre_tipo_usuario varchar(100) NOT NULL,
  CONSTRAINT pk_tipo_empleado PRIMARY KEY (id_tipo_usuario)
); 

comment on table TIPO_EMPLEADO is 'Listado de todos los tipos de empleados que hay';

/*==============================================================*/
/* Table: EMPLEADOS                                             */
/*==============================================================*/
CREATE TABLE empleados
(
  rut char(10),
  id_tipo_usuario char(10),
  nombre_usuario varchar(20),
  "password" varchar(20),
  CONSTRAINT fk_empleado_reference_socios FOREIGN KEY (rut) REFERENCES socios (rut) ON UPDATE RESTRICT ON DELETE RESTRICT,
  CONSTRAINT referencia_tipo_empleado FOREIGN KEY (id_tipo_usuario) REFERENCES tipo_empleado (id_tipo_usuario) ON UPDATE RESTRICT ON DELETE RESTRICT
) ;
comment on table EMPLEADOS is 'La lista de empleados';

The tables are created with no probs.

I created some default data in table tipo_empleado, but when i try to fill the data in the second table with the _correct_ (unless 1 != 1 or 2 != 2) data, next error appears: (it's in spanish, i'll try my best to replicate it in english)

an error has occured: 
ERROR: referencia_tipo_empleado has violated the referencial integrity - reference to the key from empleados is not found in tipo_empleado

I really don't understand what's going on ... Thougth it maybe could be powerdesigner, but it isn't ... All other foreign keys are working perfectly .. except this one ... i don't know, seems to me that everything is correct... must be something stupid, but i don't get it ... Thanks in advance