I just installed SQL Server Express 2008 R2 and I have a problem connecting to it using the SQL Server Management Studio (locally).
All SQL Server services are started
The same error can happen if your SQLEXPRESS instance is not started. To verify the service is started: - run services.msc - Look for the "SQL Server (SQLEXPRESS)" service, status should be "Started", if it is not, try to start it manually.