EP6.0 error when using windows authentication : 404 Not Found

Hi,

We have EP6.0 and can access it with or without windows authentication( without needing to log on using username and password). we have created two urls for that purpose to logon to the portal.

However, while using the windows authentication

) , we have found that, when we navigate to the content administration--> web dynpro, the error below( within sqare brackets) appears.

[404 Not Found

SAP J2EE Engine/6.40

The requested resource does not exist.

Details: Go to main page of this application! ]

The same doesn't occur when we use the basic authentication( username and password) .

Can anybody help?

Thanks

Arunabha