i know there are already many post on these. But after a skim through none of them really helps.
It was all working and all of a sudden it produce this error.
SQL Server and Web Server all functioning proberly according to the status and my check. So it has nothing to do with server going down.
SQL is 100% surely named as localhost.
So i don't know what the problem is. But it looks like many other user have experience this b4.