I've been using Entity Framework migrations for a few weeks now and I'm having a great time with. However, I've notice that every now and then Entity Framework throws an error when I try to run the 'Update-Database' command.
Whenever you get a message 'Could not load file or assembly or one of its dependencies. The system cannot find the file specified.' there are a few steps that I've noticed you can do to help work around this type of error.