mysql SELECT的奇怪错误，百思不得其解

ivanchen

mysql> select username,password from user where username='COCO';
+----------+----------------------------------+
| username | password |
+----------+----------------------------------+
| 球球 | abfd6bd1d2f47650b8f6e3cc8b478f91 |
+----------+----------------------------------+
1 row in set (0.00 sec)

相关的错误还有：
SQL_STR: select username,password from user where username='懒懒'
RESULT[0]: 玲玲

SQL_STR: select username,password from user where username='妞妞'
RESULT[0]: 皮皮

SQL_STR: select username,password from user where username='皮皮'
RESULT[0]: 妞妞

SQL_STR: select username,password from user where username='娃娃'
RESULT[0]: 晓晓

SQL_STR: select username,password from user where username='晓晓'
RESULT[0]: 娃娃

SQL_STR: select username,password from user where username='叶帆'
RESULT[0]: 远帆

SQL_STR: select username,password from user where username='酷酷'
RESULT[0]: 柯柯

SQL_STR: select username,password from user where username='远帆'
RESULT[0]: 叶帆

SQL_STR: select username,password from user where username='玲玲'
RESULT[0]: 懒懒

SQL_STR: select username,password from user where username='COCO'
RESULT[0]: 球球

SQL_STR: select username,password from user where username='蝈蝈'
RESULT[0]: 优优

SQL_STR: select username,password from user where username='乐乐'
RESULT[0]: 丽丽

SQL_STR: select username,password from user where username='球球'
RESULT[0]: COCO

SQL_STR: select username,password from user where username='死人'
RESULT[0]: 闪人

SQL_STR: select username,password from user where username='闪人'
RESULT[0]: 死人

SQL_STR: select username,password from user where username='丽丽'
RESULT[0]: 乐乐

SQL_STR: select username,password from user where username='野子'
RESULT[0]: 影子

SQL_STR: select username,password from user where username='影子'
RESULT[0]: 野子

SQL_STR: select username,password from user where username='优优'
RESULT[0]: 蝈蝈

SQL_STR: select username,password from user where username='柯柯'
RESULT[0]: 酷酷

＝＝＝＝＝＝＝＝＝＝＝
我原本以为是字符集编码的错误，可是where username='COCO'也出错，到底是怎么回事？

我现在使用的mysql版本：4.0.20，Under redhat 9
原来从3.2.23升级而来，升级前就有这样的问题，升级后还是这样的问题。

请各位大侠指教，万分感谢