Fatal process interaction

The situation:
In xterm #1: psql running, connected to database pssdb, executing an SQL select
statement.

In xterm #2: A shell script is run that pipes another select statement throug psql.

When the select statement in xterm #2 completes, the select statement being executed
in xterm #1 aborts and the following error message is output:

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.
pqReadData() -- backend closed the channel unexpectedly.
This probably means the backend terminated abnormally before or while
processing the request.
We have lost the connection to the backend, so further processing is impossible.
Terminating.

This problem is very repeatable and does not seem to depend on which UID is running
which session. They can both be postgres, or me (smw) or one of each. The one
common factor appears to be that psql is involved in both. If psql is run in
interactive mode in both windows, then \q is issued in one of the windows, both psql
sessions will terminate.

Any ideas?
--
Steven M. Wheeler
UNIX Engineering
The SABRE Group
(918) 292-4119
(918) 292-4165 FAX