MSPOSTGISLayerOpen -- shared connection not available

[Steve W]

Am unable to render a map with a POSTGIS layer.

Archive and g**gle searches come up almost empty on this one.

Architecture:  ms4w/Apache 2.0.54/PHP4.3.11/mapserv4.6

Layer exists, can be queried spatially and non-spatially outside of
mapserver, and can be displayed in QuantumGIS.  So I believe the data is fine.

Map file snippet looks like this:

LAYER
 NAME "country"
 CONNECTIONTYPE postgis
 CONNECTION "dbname=world user=postgres password=XXXXX server=localhost
port=5432"
 DATA "geom from public.cntry2"
 DEBUG TRUE

(or I can provide user=nobody)

Apache error log looks like this:

[error] [client 127.0.0.1] msPOSTGISLayerOpen called datastatement: geom
from public.cntry2\r, referer: http://localhost/world/index.phtml
[error] [client 127.0.0.1] MSPOSTGISLayerOpen -- shared connection not
available.\r, referer: http://localhost/world/index.phtml

[Tue Feb 28 14:09:40 2006] [error] [client 127.0.0.1]
FAILURE!!!msPOSTGISLayerClose datastatement: geom from public.cntry2\r,
referer: http://localhost/world/index.phtml
[Tue Feb 28 14:09:40 2006] [error] [client 127.0.0.1] msPOSTGISLayerClose --
layerinfo is  NULL\r, referer: http://localhost/world/index.phtml


Found a suggestion to manipulate POSTGRESQL's pg_hba.conf configuration file
to replace authorization 'md5' with 'trust' for all users on the localhost.
 However when doing so, either a)all connections to the postmaster fail; or
b) problem continues.

Have set the postgresql.conf listen_address variable = '*' as suggested to
allow connections from all hosts.

Thank you for any insights
-steve