Have you setup Kerberos? It sounds like you might not have Kerberos setup correctly (Kerberos is probably required if you want to pass through user credentials from SharePoint through to SSRS).

• http://technet.microsoft.com/en-us/library/bb283324.aspx
• http://msdn.microsoft.com/en-us/library/bb326356.aspx
• http://blogs.msdn.com/b/martinkearn/archive/2007/04/23/configuring-kerberos-for-sharepoint-2007-part-1-base-configuration-for-sharepoint.aspx

Have you setup Kerberos? It sounds like you might not have Kerberos setup correctly (Kerberos is probably required if you want to pass through user credentials from SharePoint through to SSRS).

• http://technet.microsoft.com/en-us/library/bb283324.aspx
• http://msdn.microsoft.com/en-us/library/bb326356.aspx
• https://web.archive.org/web/20160228171347/http://blogs.msdn.com:80/b/martinkearn/archive/2007/04/23/configuring-kerberos-for-sharepoint-2007-part-1-base-configuration-for-sharepoint.aspx