Foreign key constraint referencing a parent table

Hi,

I have a problem when inserting rows into my table tblfactuurpost that
references a table tblfactuur which is a parent to tblclientfactuur.
The actual row is inserted into tblfactuur.

The problem is that i cannot insert the row into tblfactuurpost (which
references the parent table tblfactuur) because PSQL complains the
referencing ID (2) is missing while it is actually *not* missing at all.

Thanks to anyone who can shed some light ...

I have the following table set-up:

CREATE TABLE tblfactuur (
id serial PRIMARY KEY,
number int NOT NULL,
year int NOT NULL CHECK (year>=1900 AND year<=2999),

vanaf date NOT NULL,
tot date NOT NULL CHECK (tot > vanaf),

total int -- totaalbedrag in centen
);

CREATE TABLE tblclientfactuur (
client int NOT NULL REFERENCES tblclient (id) ON DELETE RESTRICT
, PRIMARY KEY (id)
) INHERITS (tblfactuur);

CREATE TABLE tblfactuurpost (
id serial PRIMARY KEY,
factuur int NOT NULL REFERENCES tblfactuur (id) ON DELETE CASCADE
DEFERRABLE,

omschrijving varchar(128),

btw smallint DEFAULT 19, -- standaard 19% btw
aantal decimal(8,1) NOT NULL CHECK (aantal >= 0), -- aantal
perstuk int NOT NULL CHECK (perstuk >= 0), -- bedrag per stuk in
centen
amount int NOT NULL CHECK (amount >= 0), -- totaal bedrag in centen

position smallint CHECK (position >= 0)
);

This is the data in tblfactuur:

(db)=> select * from tblfactuur;
id | number | year | vanaf | tot | total
----+--------+------+------------+------------+--------
2 | 1 | 2010 | 2010-03-01 | 2010-04-01 | 397800
(1 row)

I try to insert:

insert into tblfactuurpost (factuur, omschrijving, btw, aantal, perstuk,

amount, position)
select ?, ?, ?, ?, ?, ?, count(*) from tblfactuurpost where factuur

= ?;
parameters: (2, Gespecialiseerde 24 uur zorg ma. t/m vr., 19, 156, 1425,

397800, 2)

Regards, David