Cannot change password with OWA (Error number: -2147024891)

The OWA change password function not working. It returns the "Error number: -2147024891".

After searching from the web, the authentication account of the IIS may be the source of the problem. I follow the suggestion of this site to create a new user for the authentication: (http://forums.msexchange.org/Owa_Error_-2147024891_while_changing_password/m_170043200/tm.htm)

Mmmu...the problem seems to be solved, partly.

More relevant sites, although not the solution to my problem:

http://www.veloci.dk/forum/topic.asp?TOPIC_ID=127
http://support.microsoft.com/kb/301428
http://www.msexchange.org/tutorials/Securing-Exchange-Server-2003-Outlook-Web-Access-Chapter5.html

The problem is solved partly because other accounts can change the password through OWA but NOT MY OWN ACCOUNT!! :<

So...still troubleshooting (due to the Group Policy? or other settings of my account?).

Anyway, at least the boss' concern is solved. Thanks God!