Still expired password changing using IISADMPWD with IIS6

Configured IIS6 on W2003 using Microsoft document :
- created iisadmpwd virtual directory
- registered iispwdchg.dll
- configured metabase PasswordChangeFlags

Users can manually get page aexp2b.asp but when a user with an expired
password tries to acess the web site he isn't redirected to the changing
password page. The browser keeps asking for a valid user/password and the
IIS logs 401 error. The web server belongs to a AD domain.

Have done the same configuration in a IIS6 on a W2003 box not in a domain
(using local computer accounts) and it works as expected. What am I missing
here ?

Thanks in advance

.