Cache lookup failed for type for Slony-I tables

Hello.

I'm defining a replication schema with Slony-I, but I get this error: "cache
lookup failed for type 3044543".

postgres7 error: [-1: ERROR: cache lookup failed for type 3044543
CONTEXT: SQL statement "INSERT INTO _bd_cluster.sl_log_1 (log_origin,
log_xid, log_tableid, log_actionseq, log_cmdtype, log_cmddata) VALUES

(1, $1, $2, nextval('_mic_cluster.sl_action_seq'), $3, $4);"] in
EXECUTE("UPDATE TGEN_SESSION SET FECHA_SALIDA = '2009-05-15 08:57:08',
ESTADO = 'INACTIVO' WHERE SESSION_ID = 'jm35et6hq0tceig413r0oevai0'")

I don't know exactly what that could mean, but the database was in a
production environment so I stopped the 'slon' demon and dropped the
replication schema.

Now, I've been looking in the web all morning for an answer to this problem
and I found some threads about it, but it seems that none of the
recommendations are very clear about what should be done to fix this.

Here are some of the threads I've read:

Cache lookup failed for function (they said that it could be an interference
in pg_* tables):
http://pgfoundry.org/pipermail/brasil-usuarios/20060927/002693.html (in
portuguese)

Cache lookup failed for type (there's a message from Jaime Casanova, saying
that is all about a BUG :s):
http://archives.postgresql.org/pgsql-admin/2005-12/msg00232.php

Cache lookup failed for type (Postgis related):
http://postgis.refractions.net/pipermail/postgis-users/2008-September/021271.html

According to this threads, I could say that is not an Slony related issue,
but it seems estrange that the error raises up just for those tables.

Now, checking the logs, I've seen another error about the WAL handling, I
don't know if that could be affecting the server:

LOG: archive command failed with exit code 1
DETAIL: The failed archive command was: cp -i pg_xlog/000000010000003200000050
/var/lib/pgsql/logs/wal/000000010000003200000050
WARNING: transaction log file "000000010000003200000050" could not be
archived: too many failures

PostgreSQL version: 8.3.7
Slony-I version: 1.2.15

Thanks in advance, Luis.

--
Luis D. García M.

Telf: (+58) 2418662663
Cel.: (+58) 4123497674