duplicate key

Hello eveybody,

We are trying to REINDEX a database, but we encounter some strange problem.
We have the message "Cannot insert a duplicate key into index
synd_article_pkey".
It appears that we have duplicate key in the base, with exactly the
same informations.
We then did the above query:
"select id_synd_art from synd_article group by id_synd_art having
count(id_synd_art)>1".
id_synd_pkey is the primary key on id_synd_art, a not null field with
default nextval('"synd_article_id_seq"'::text)

By example, we can have the above informations, when we do a select
on one of the key given by the previous query :
11470 | actualite_generale/une/ | 2002-08-01 21:00:00-01 | La Une |
020802132619bsbfe0
11470 | actualite_generale/une/ | 2002-08-01 21:00:00-01 | La Une |
020802132619bsbfe0

We have exactly the same things in the base.
Actually, we have 221 duplicate keys in the table (65000 records)

We can't do REINDEX on the base and VACUUM. So the base is growing
and growing and so...

Any idea about this problem ?

Thanx,
Pascal.