Debugging I/O errors occured while reading from backend

I'm getting exceptions about "An I/O error occured while reading from
backend" occuring under load.

From reading in the archives,
<http://archives.postgresql.org/pgsql-jdbc/2001-04/msg00050.php> and
<http://archives.postgresql.org/pgsql-general/2001-07/msg01271.php> the
primary suggestion is to enable postmaster logging.

I had enabled log_connections, but that didn't show anything.

I'm asking rather than just dialing up the log verbosity because this
is occurring in a production environment and I didn't want to slow them
down with overly verbose logging.

Any help is appreciated. Thanks!!
-peter

Below are my settings from postgresql.conf:

Things i changed:

syslog = 2
syslog_facility = 'LOCAL5'

Defaults:

#
# Message display
#
#server_min_messages = notice # Values, in order of decreasing detail:
# debug5, debug4, debug3, debug2,
debug1,
# info, notice, warning, error, log,
fatal,
# panic
#client_min_messages = notice # Values, in order of decreasing detail:
# debug5, debug4, debug3, debug2,
debug1,
# log, info, notice, warning, error
#silent_mode = false

#log_connections = false
#log_pid = false
#log_statement = false
#log_duration = false
#log_timestamp = false

#log_min_error_statement = error # Values in order of increasing
severity:
# debug5, debug4, debug3, debug2,
debug1,
# info, notice, warning, error,
panic(off)