DELETE statement KILL backend

 Hello all,

 I have a strange problem that I can't understand.
 I have been my PostgreSQL-6.3.2 on Linux-ELF-2.0.34 working without any problem for many
 months. This morning I can't DELETE anymore.
 If I try to delete a row from any table I have this message:

 PGexec() -- Request has sent to backend, but backend closed the
 channel before responding.
 This probably means the backend terminated abnormally before or while
 processing the request.

 and then the backend dies.

 I tried every statement as:
 INSERT
 UPDATE
 SELECT
 DROP TABLE
 and all of them works but DELETE,

 I tried also VACUUM without success.

 PLEASE help me !!

 Best regards,
    Jose'                          mailto:sferac@bo.nettuno.it