corruption since 7.4.13 update ?

Hello,
I'e got a very strange (scary) problem.
Look at that :

itu_test-# \d
ERROR: cache lookup failed for relation 1024
itu_test=# \q

[user(at)varese ~]$ psql -h pisa itu_test
itu_test=# \d
ERROR: cache lookup failed for relation 1024

itu_test=# select * from zones;
zone_id | code | region_id
---------+------+-----------
1 | can | 1
(1 row)

itu_test=# \d zones;
ERROR: cache lookup failed for relation 1024

itu_test=# drop table zones cascade;
NOTICE: drop cascades to constraint fk894f2383638e21c5 on table
zones_localized
NOTICE: drop cascades to constraint fk2f1483ad638e21c5 on table
resources_zones
NOTICE: drop cascades to constraint fk6ca02e89638e21c5 on table
regulator_zones
NOTICE: drop cascades to constraint fkfe5f0292638e21c5 on table regulators
DROP TABLE

itu_test=# \d
ERROR: cache lookup failed for relation 1024

itu_test=# VACUUM ANALYZE;
ERROR: could not open segment 1 of relation "pg_class_oid_index"
(target block 1702494308): No such file or directory

itu_test=# REINDEX DATABASE itu_test;
NOTICE: table "pg_class" was reindexed
(...)
NOTICE: table "pg_language" was reindexed
ERROR: could not read block 81235 of relation "pg_largeobject":
Input/output error

itu_test=# \d
ERROR: cache lookup failed for relation 1024

itu_test=# reindex table pg_class;
REINDEX

itu_test=# VACUUM ANALYZE;
WARNING: relation "pg_class" TID 12638/1: OID is invalid
(...)
WARNING: relation "pg_class" TID 12638/24: OID is invalid
ERROR: cannot compare arrays of different element types

itu_test=# \d
List of relations
Schema | Name | Type | Owner
--------+------------------------------+----------+----------
public | categories | table | soft_itu
(...)
public | zones_localized | table | soft_itu
(51 rows)