psql错误信息显示为？

在ubuntu10.4下，使用psql，出错时，显示信息为？？？号，请问如何处理？
/etc/postgresql/8.4/main/postgresql.conf的相关设置是：

client_encoding = UTF8                # actually, defaults to database
                                        # encoding

# These settings are initialized by initdb, but they can be changed.
lc_messages = 'zh_CN.UTF-8'                        # locale for system error message
                                        # strings
lc_monetary = 'zh_CN.UTF-8'                        # locale for monetary formatting
lc_numeric = 'zh_CN.UTF-8'                        # locale for number formatting
lc_time = 'zh_CN.UTF-8'                                # locale for time formatting

报错信息如下：
sup@my-desktop:~$ psql -U postgres
psql: ????:  ?? "postgres" Ident ????

-----------------------------
请问要怎么设置菜可以把错误信息显示出来？最好是显示为英文。我在lc_messages那里设置为en_US或en_US.UTF-8都不行，还是显示为？号。

谢谢！

忘了贴上我的locale，补上
sup@my-desktop:~$ locale
LANG=zh_CN.UTF-8
LANGUAGE=en
LC_CTYPE=zh_CN.UTF-8
LC_NUMERIC="zh_CN.UTF-8"
LC_TIME="zh_CN.UTF-8"
LC_COLLATE="zh_CN.UTF-8"
LC_MONETARY="zh_CN.UTF-8"
LC_MESSAGES="zh_CN.UTF-8"
LC_PAPER="zh_CN.UTF-8"
LC_NAME="zh_CN.UTF-8"
LC_ADDRESS="zh_CN.UTF-8"
LC_TELEPHONE="zh_CN.UTF-8"
LC_MEASUREMENT="zh_CN.UTF-8"
LC_IDENTIFICATION="zh_CN.UTF-8"
LC_ALL=