Linked Server Error

To whom it may concern:

I am running SQL Server on Windows 2003 R2 (32-bit) connecting to
Postgres on SCO Unix. I have installed the ODBC driver
(psqlodbc_08_03_0100) and can query the tables in Postgres using
OPENQUERY from SQL Server. Everything works great where this is
concerned.

The issue I am having involves calling a Postgres Function from SQL
Server. The user ID that I am using to connect to Postgres is a
SuperUser and the function I created in Postgres is accepted without a
error (in pgAdmin III).

The Function:

-------------------------------------------------------

CREATE OR REPLACE FUNCTION mssql_test()

RETURNS integer AS

$BODY$DECLARE

retval bigint;

BEGIN

retval:=(SELECT count(*) FROM dminvoice);

return retval;

END;$BODY$

LANGUAGE 'plpgsql' VOLATILE;

ALTER FUNCTION mssql_test() OWNER TO testuser;

GRANT EXECUTE ON FUNCTION mssql_test() TO public;

GRANT EXECUTE ON FUNCTION mssql_test() TO testuser;

The way I am calling the function is as follows:

Function Call:

-------------------------------------------------------

EXEC [PostgreSQL].dta.testuser.mssql_test (ODBC
Connection.Database.User.Function Name)

The response I get from Postgres is:

Error:

-------------------------------------------------------

OLE DB provider "MSDASQL" for linked server "PostgreSQL" returned
message "ERROR: syntax error at or near "1";

Error while executing the query".

Msg 7212, Level 17, State 1, Line 1

Could not execute procedure 'mssql_test' on remote server 'PostgreSQL'.

Any help you can provide on this would be greatly appreciated.

Thanks in advance,

Jeff