PL/Python error fetching next item from iterator

Hello All
I have problem when running PL/Python code in my customer machine, the
python code run well on my dev machine.

My Dev machine PostgreSQL 9.0.6, compiled by Visual C++ build 1500,
64-bit, Python
2.6 (r26:66721, Oct 2 2008, 11:06:43) [MSC v.1500 64 bit (AMD64)] on
win32, pyodbc-2.1.11.win-amd64-py2.6
My Customer machine PostgreSQL 9.0.8, compiled by Visual C++ build 1500,
64-bit , Python 2.6 (r26:66721, Oct 2 2008, 11:06:43) [MSC v.1500 64 bit
(AMD64)] on win32, pyodbc-2.1.11.win-amd64-py2.6

Here is my 2 function

CREATE TYPE dmkh_return AS
(ma_kh character varying,
ten_kh character varying,
ten_kh2 character varying,
dia_chi character varying,
ma_so_thue character varying,
loai_kh smallint,
nh_kh1 character varying,
nh_kh2 character varying,
nh_kh3 character varying,
status character varying);
ALTER TYPE dmkh_return OWNER TO postgres;

CREATE OR REPLACE FUNCTION list_khachhang()
RETURNS SETOF dmkh_return AS
$BODY$
import pyodbc
cnxn = pyodbc.connect('DRIVER={SQL
Server};SERVER=127.0.0.1,2205;DATABASE=TEST;UID=itg;PWD=')
dbcursor = cnxn.cursor()
dbcursor.execute("select ma_kh, dbo.ff_v2u(ten_kh) as ten_kh, '' as
ten_kh2, '' as dia_chi, '' as ma_so_thue, CASE WHEN loai_kh IS NULL THEN 0
ELSE loai_kh END as loai_kh, nh_kh1, nh_kh2, nh_kh3, '1' as status from
dmkh")
rows = dbcursor.fetchall()
for row in _rows:
yield row
$BODY$
LANGUAGE plpythonu VOLATILE
COST 100
ROWS 1000;
ALTER FUNCTION list_khachhang() OWNER TO postgres;

==================

CREATE TYPE dmdv_return AS
(ma_dv character varying,
ten_dv character varying,
ten_dv2 character varying,
nh_dv1 character varying,
nh_dv2 character varying,
nh_dv3 character varying,
status character varying);
ALTER TYPE dmdv_return OWNER TO postgres;

CREATE OR REPLACE FUNCTION list_dichvu()
RETURNS SETOF dmdv_return AS
$BODY$
import pyodbc
cnxn = pyodbc.connect('DRIVER={SQL
Server};SERVER=127.0.0.1,2205;DATABASE=TEST;UID=itg;PWD=')
dbcursor = cnxn.cursor()
dbcursor.execute("select ma_dv, dbo.ff_v2u(ten_dv) as ten_dv,
dbo.ff_v2u(ten_dv2) as ten_dv2, nh_dv1, nh_dv2, nh_dv3, '1' as status from
dmdv")
rows = dbcursor.fetchall()
for row in rows:
yield row
$BODY$
LANGUAGE plpythonu VOLATILE
COST 100
ROWS 1000;
ALTER FUNCTION list_dichvu() OWNER TO postgres;
====================

When i run
SELECT * FROM list_dichvu() : It is Ok

But error happen when I run
SELECT * FROM list_khachhang()

ERROR: error fetching next item from iterator
CONTEXT: PL/Python function "list_khachhang"

********** Error **********

ERROR: error fetching next item from iterator
SQL state: 22000
Context: PL/Python function "list_khachhang"

How to fix error. Please help me. Thanks in advance. Sorry for my English

Tuan Hoang Anh