Corrupted db?

We got a problem ticket from the customer.
Messages in the error_log indicated problem trying to insert
a duplicate value into a table.
Looking at the database (v.7.3.2 on Solaris) I'm puzzled with this:

syncdb=# \d
ERROR:  Cache lookup failed for relation 17075

syncdb=# \di
ERROR:  Cache lookup failed for relation 17081

syncdb=# \d property_types;
ERROR:  Cache lookup failed for relation 17075

syncdb=# \d public.property_types          Table "public.property_types"  Column    |          Type           |
Modifiers
 
-------------+-------------------------+-----------id          | integer                 | not nullname        |
charactervarying(256)  | not nullstamp       | date                    | not nulldescription | character varying(1024)
|
 
Indexes: pt_pk primary key btree (id),        pt_name_uid_uk unique btree (name)


syncdb=# SET search_path = public, pg_catalog;
SET
syncdb=# \d property_types;
ERROR:  Cache lookup failed for relation 17075

syncdb=# select * from pg_namespace ; nspname   | nspowner | nspacl 
------------+----------+--------pg_catalog |        1 | {=U}pg_toast   |        1 | {=}public     |        1 |
{=UC}pg_temp_1 |        1 | 
 
(4 rows)

syncdb=# select * from property_types;id | name | stamp | description 
----+------+-------+-------------
(0 rows)

INSERT INTO property_types (id, name, description, stamp)
VALUES (nextval('pt_seq'), 'FROM_RELATIONSHIP',       'Describes the relationship of ...', date('today'));

ERROR:  Cannot insert a duplicate key into unique index pt_name_uid_uk
---------------------------------------------

I can only guess that something is corrupted.
What could lead to that?
Can this can be prevented or repaired?

Thank you,
Mike.