My son plays on OS X as a restricted user. Every now and then when starting, the Launcher pops up with a window "downloading runtime" and downloading roughly 120MB - I'm guessing that it has something to do with new launcher updates being released. Download finishes, launcher disappears, nothing else happens. When starting the launcher again, the same download starts again, finishes, launcher disappears, nothing else happens. Launcher is basically broken, until I login (I'm admin user) and run the launcher once. Then it downloads, finishes, and launches. Once that's done and I log off again, my son can start the launcher without problems.