BUG #4535: Foreign Key Constraints are not respected

The following bug has been logged online:

Bug reference:      4535
Logged by:          PRIME
Email address:      g.prime@aeschemunex.com
PostgreSQL version: 8.3.5
Operating system:   Windows XP
Description:        Foreign Key Constraints are not respected
Details:

Hello,

I had last week a problem with postgresql 8.3.4, one table named "xxxx" have
a foreign key pointing to a key (integer) of a table named "yyyy",
constraints are on these tables to have only valid "yyyy" keys in "xxxx"...
naturally...

So after one or two days of using my software (that uses Npgsql to make the
queries) i had a row in "xxxx" that points to a non present key of "yyyy"...
This is unbelivable but true.... See :
http://gildas.prime.free.fr/postgresql/postgresql.JPG

So di erase my installation and made a new one with 8.3.5, same thing
happend...

I had made a dump of my database and try to restore it in a new database,
and then restoration fails because constraints are not respected...
Un-be-li-va-ble.... :(
See : http://gildas.prime.free.fr/postgresql/constraint.JPG

Is this case already happened to somebody ?

PS1 : Sorry for my (bad) english...
PS2 : I have the database backup and the data directory if it can be
helpful.