BUG #2210: an update query bug with a table but not with your backup

The following bug has been logged online:

Bug reference: 2210
Logged by: Ricardo Solanilla
Email address: abasoft(at)ciudad(dot)com(dot)ar
PostgreSQL version: 8.0
Operating system: Windows XP
Description: an update query bug with a table but not with your
backup
Details:

i try those querys, they are too similars and simple.. but the first work
fine but the second don't. Then i do a backup with insert clauses and put
both tables in another empty database, but now work fine the second query
too. it's depending on data i think, but i've done a backup and it have the
same number of rows..
If you like to study that i can send you the entire backup of database.

I'm system engenieer and hope i know that i know !! :-)

Tia.

update ctem set idctb = (SELECT CreConcep.DeudaIdctb from creconcep INNER
JOIN CTEM C1 ON
(c1.codcreconcep = creconcep.cod) WHERE C1.ID = CTEM.ID)
where ctem.tipovalt = 'CC-M' and CodCreConcep is not null

update ctem set idctb = (SELECT CreConcep.DeudaADevIdctb from creconcep
INNER JOIN CTEM C1 ON
(c1.codcreconcep = creconcep.cod) WHERE C1.ID = CTEM.ID)
where ctem.tipovalt = 'CC-A' and CodCreConcep is not null