I am running SSRS for MSSQL 2008 with an external URL. When a user logging in from a computer outside of the domain pulls up the Report Manager interface, they are prompted to login. They are able to use their domain credentials and see the reports they have been granted access to. The problem is that when they open Report Builder, the user is not prompted for their login again and Report Builder assumes the credentials of the user that they used to log in to their computer and not the domain user supplied to Report Manager. I have been unable to figure out how to force Report Builder to prompt for login credentials. Is this possible? If so, how would I go about doing this?