From a Windows XP machine, I get the following error when trying to edit/access/run a report in Visual Studio 2005. Data source is on SQL Server 2005 using mixed mode authentication.
Login failed for user ''. The user is not associated with a trusted SQL Server connection. (Microsoft SQL Server, Error: 18452)
This works fine for the same user on a different PC running Windows 7. So we are thinking there is some local setting causing incorrect login to be passed instead of the expected Windows login. NOTE: login to the source database using SQL Server Management Studio and Windows authentication works correctly on the same PC.