How can I fix the T-SQL editor in VS 2012 after installing SQL Server 2012 SP1?

Question

I can suddenly no longer open .sql files in VS 2012 by simply double clicking in the Solution Explorer. I get the error message:

Unable to open Transa

Answer 1

Almost a year later, but I found the answer from joerage to be more helpful.

Default to the T-SQL Pane view within Visual Studio 2012 Database Project