Well tbh I have no Idea whats going wrong, so I have to ask a couple of questions in order to come closer to the problem.
- Are you running on Windows 2003 ServicePack 1 already?
- Are any detailed error's displayed on the webpage? From the http code it says Access Denied to the Passwordmanager.dll
- You aren't prompted for a username or password before this error comes?
Have you also double checked the Anonymous Authentication Options? Maybe there is something wrong with the default settings.