possible bug in SELECT with UNION

Hi,

I have PostgreSQL 8.0.3 for Windows XP and i have in attach the database
with problem.

The problem occour with this SQL

select proextra.data as data, 0 as codigo, proextra.motivo as nome, 'X'
as tipo, proextra.qtd, 0 as valor_u, 0 as cod_v from proextra where
proextra.data>=to_date('28/04/2006','dd/mm/yyyy') and
proextra.data<=to_date('28/04/2006','dd/mm/yyyy') and
proextra.lancado='S' and proextra.codigo=1106 union
select entrad1.emissao as data, entrad1.cod_f as codigo, entrad1.nome_f
as nome, 'E' as tipo, entrad2.qtd, entrad2.preco_u as valor_u, 0 as
cod_v from entrad1, entrad2 where entrad1.numero=entrad2.numero and
entrad1.emissao>=to_date('28/04/2006','dd/mm/yyyy') and
entrad1.emissao<=to_date('28/04/2006','dd/mm/yyyy') and
entrad1.lancado='S' and entrad2.cod_p=1106

The result correct is two (2) rows in table proextra but result one (1)
row!!!

If i do:

select proextra.data as data, 0 as codigo, proextra.motivo as nome, 'X'
as tipo, proextra.qtd, 0 as valor_u, 0 as cod_v from proextra where
proextra.data>=to_date('28/04/2006','dd/mm/yyyy') and
proextra.data<=to_date('28/04/2006','dd/mm/yyyy') and
proextra.lancado='S' and proextra.codigo=1106
I receive two (2) rows if i union with other table i receive one (1) row!!!

This is a bug or my SQL is not correct????

For create this database

create database pcpneus;
create user loja001 with password 'test';
psql pcpneus "postgres" < pcpneus.txt

Thanks,

Dario Basso Cardoso
Brazil

Ps. How i send backup for this database for analize?