“Cheatin’ uh?” error message on multple theme directories

In my wp-config.php I’ve added another theme directory; register_theme_directory( dirname( __FILE__ ) . '\..\themes' );. I’m not sure if this is the correct place to add it.

When I then try to preview my theme, I just get the error message Cheatin’ uh?.
Does anyone know how to fix this?

Make sure that you’re logged in as admin

1. Goto Settings
2. General Settings
3. Make sure that your site URL is “http://yoursitehere.com”

If you have previously changed that it could cause you problems all across the board.