ASP.NET/SQL Server: Failed to generate a user instance of SQL Server; Login failed for user ‘NT AUTHORITY\NETWORK SERVICE’

While working on an ASP.NET 4.0 web application that uses the built-in Membership tools, I recently encountered the above two errors which prevented the site from working until sorted. I suspect the errors were triggered by the SP1 update to SQL Server 2008, as the application was working fine prior to my finally applying the […]