When you say the files won't load, are you talking about when you select Misty's Place to fly from on the main menu and then it changes to next the screen, the one with the progress bar, then nothing happens, and the progress bar just sits at zero? This is the only place that Misty's, or any other scenery for that matter, actually "loads." Can you post a screenshot of where FSX just hangs up and sits idle?
Also, if you installed it properly, and in the same folder where you have all of your other addon scenery placed, and Misty's won't load because of some sort of configuration error in the scenery.cfg file, then you'd get an error message when FSX is booting up. Lacking that, then you probably aren't waiting long enough for Misty's to actually load. It will take a LONG time to load in plain vanilla FSX, as I stated before.