pg_dump failed

hello,

i've got the following problem:
OS - Solaris 8/9 on Sun SPARC
PGSQL 7.1.3

when i try to dump the database with pg_dump command i've got the
following error:

--  last builtin oid is 18539
--  reading user-defined types
--  reading user-defined functions
--  reading user-defined aggregates
--  reading user-defined operators
--  reading user-defined tables
getTables(): SELECT failed.  Explanation from backend: 'pqReadData() --
backend
closed the channel unexpectedly.
         This probably means the backend terminated abnormally
         before or while processing the request.
'.

the same error appears when a try to display the database schema using
\d in psql shell e.g.

$ psql -U user db
psql# \d
getTables(): SELECT failed.  Explanation from backend: 'pqReadData() --
backend
closed the channel unexpectedly.
         This probably means the backend terminated abnormally
         before or while processing the request.
'.

but when a type:
psql# \d table_name
everything works fine ...

what's wrong ?
pg_dump is really really really important for me ... thanx in advance ...

--
Milan Krajnak
senior software architect
e-mail: milan_krajnak@abilitydev.com
phone: +421 2 50267546
fax  : +421 2 50267500
Ability Development SK
http://www.abilitydev.com