I cant get walking dead to work!
 

I have completed all 4 episodes, so i was up to episode 2 on a new game before it started to rewind my progress. Then the next time i tried to play my game, a caption came up saying do you want to rewind and lose your progress or not, but no matter what i do if i say yes or no nothing happens. it goes blank and it freezes, i cant get back to my desk top or to the menu screen ... the only way i can make it stop is to turn my computer off again. I really need some help and the place i bought it from stream hasnt been of much help. I really want to play this game, so is there anything i can do to get it back to normal ? i an playing on a mac btw.