problems with pg_dump... with postmaster really

I have found that the postmaster is dying very offen lattly, and yesterday I
got this error on a pg_dumpall:

connected to template1...
dumping database "horde"...
dumping database "lismarch"...
pg_dump: NOTICE: Message from PostgreSQL backend:
The Postmaster has informed me that some other backend
died abnormally and possibly corrupted shared memory.
I have rolled back the current transaction and am
going to terminate your database system connection and exit.
Please reconnect to the database system and repeat your query.
pg_dump: query to obtain list of operators failed: server closed the
connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
pg_dump failed on lismarch, exiting

I got these kind of errors in normal conections too. Any idea?

--
Porqué usar una base de datos relacional cualquiera,
si podés usar PostgreSQL?
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Martín Marqués | mmarques(at)unl(dot)edu(dot)ar
Programador, Administrador, DBA | Centro de Telematica
Universidad Nacional
del Litoral
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