Just in case anyone else has this problem: I use the Pluralsight offline player to watch videos on my 1 hour train ride to and from work. I noticed that the player wouldn't load the course list intermittently. Then I noticed that it would load the coarse list if I had internet access, which defeats the purpose of an offline player.
After a little thought, I figured out that the Pluralsight offline player uses Silverlight, but it doesn't load it. Internet Explorer can load it. So if it is not showing your course list, launch IE, then launch the player. Your course list will show up afterwards.