关于PL/SQL与iSQL PLUS查询时出现方框与问号的问题

请问一个关于字符集的问题,让我很郁闷.我在PL/SQL、SqlPlus、Sql 等查询时，汉字字符正常显示。在ＯＥＭ企业管理器下查看数据出现在？？问号，在iSQL Plus 浏览器与VS 2005查询调用数据时出现方框，请问是怎么回事啊。我详细描述一下我的配置：
SQL> select * from nls_database_parameters;PARAMETER                      VALUE
------------------------------ -----------------------------
NLS_LANGUAGE                   AMERICAN
NLS_TERRITORY                  AMERICA
NLS_CURRENCY                   $
NLS_ISO_CURRENCY               AMERICA
NLS_NUMERIC_CHARACTERS         .,
NLS_CHARACTERSET               US7ASCII
NLS_CALENDAR                   GREGORIAN
NLS_DATE_FORMAT                DD-MON-RR
NLS_DATE_LANGUAGE              AMERICAN
NLS_SORT                       BINARY
NLS_TIME_FORMAT                HH.MI.SSXFF AMPARAMETER                      VALUE
------------------------------ -----------------------------
NLS_TIMESTAMP_FORMAT           DD-MON-RR HH.MI.SSXFF AM
NLS_TIME_TZ_FORMAT             HH.MI.SSXFF AM TZR
NLS_TIMESTAMP_TZ_FORMAT        DD-MON-RR HH.MI.SSXFF AM TZR
NLS_DUAL_CURRENCY              $
NLS_COMP                       BINARY
NLS_LENGTH_SEMANTICS           BYTE
NLS_NCHAR_CONV_EXCP            FALSE
NLS_NCHAR_CHARACTERSET         AL16UTF16
NLS_RDBMS_VERSION              10.2.0.1.0
//以下为客户端信息
SQL> select * from nls_instance_parameters;PARAMETER                      VALUE
------------------------------ -------------
NLS_LANGUAGE                   AMERICAN
NLS_TERRITORY                  AMERICA
NLS_SORT
NLS_DATE_LANGUAGE
NLS_DATE_FORMAT
NLS_CURRENCY
NLS_NUMERIC_CHARACTERS
NLS_ISO_CURRENCY
NLS_CALENDAR
NLS_TIME_FORMAT
NLS_TIMESTAMP_FORMATPARAMETER                      VALUE
------------------------------ -------------
NLS_TIME_TZ_FORMAT
NLS_TIMESTAMP_TZ_FORMAT
NLS_DUAL_CURRENCY
NLS_COMP
NLS_LENGTH_SEMANTICS           BYTE
NLS_NCHAR_CONV_EXCP            FALSE
说明：数据库字符集为： US7ASCII而注册表配置也一样。这是怎么回事啊。我等到交软件啊。急用～～～～