When ever i try to log onto Dark Messiah it loads normally till it's about to start then a "Validating Steam File" Message pops up and after that the game wont start...anyone know why by any chance?

When it is validating the games files, let it proceed till it is finished, with a message about the result that it's OK.
If the game won't start after that, it can have many reasons, as explained in this thread.
If you want my active help, follow my sig.