ERROR: cache lookup for userid 26 failed

Greetings,


Does anyone know what is this error?

ERROR:  cache lookup for userid 26 failed

Some system tables are inacessible in my database but I can access others. I tried to check pg_tables, but it's blocked
:

persona=> select * from pg_tables;
ERROR:  cache lookup for userid 26 failed
persona=>

The table pg_class tells me that I'm the user of the table (me, postgres user), but always I get this msg. What can be
doneto kick it out? 

persona=>  select * from pg_class
persona-> ;
             relname             | reltype | relowner | relam | relpages | reltuples | rell
ongrelid | relhasindex | relisshared | relkind | relnatts | relchecks | reltriggers | reluk
eys | relfkeys | relrefs | relhaspkey | relhasrules | relacl
---------------------------------+---------+----------+-------+----------+-----------+-----
---------+-------------+-------------+---------+----------+-----------+-------------+------
----+----------+---------+------------+-------------+--------
 pg_type                         |      71 |       26 |     0 |        2 |       122 |
       0 | t           | f           | r       |       16 |         0 |           0 |
  0 |        0 |       0 | f          | f           |
 pg_attribute                    |      75 |       26 |     0 |        6 |       461 |
       0 | t           | f           | r       |       15 |         0 |           0 |
  0 |        0 |       0 | f          | f           |
 pg_proc                         |      81 |       26 |     0 |       26 |      1083 |
       0 | t           | f           | r       |       16 |         0 |           0 |
  0 |        0 |       0 | f          | f           |

 tele_fidel_hierarq              |       0 |       26 |     0 |      176 |      6592 |
       0 | t           | f           | r       |        7 |         0 |           1 |
  0 |        0 |       0 | f          | f           |
 tipo_atendimento                |       0 |       26 |     0 |       10 |      1000 |
       0 | t           | f           | r       |        3 |         0 |           2 |
  0 |        0 |       0 | f          | f           |
(69 rows)


My linux users are ok. Postgres has 26 as user_id.

[postgres@bxsgalena postgres]$ cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
...
postgres:x:26:26:PostgreSQL Server:/home/postgres:/bin/bash


[postgres@bxsgalena postgres]$ cat /etc/group
root:x:0:root
...
postgres:x:26:


The database was working very well, but I don't know what was done to it, because another guy did the last maintenance.

That's all for now. Thanks in advance and my best regards!