After I have played the game (closed it and reopened it) in full screen three times it won't load anymore.

After I have played the game (closed it and reopened it) in full screen three times it won't load anymore. It just loads the Mojang start screen for about 15 seconds then crashes. And I have it has done this three times now. To fix it I have to make a new account on my computer and reinstall it. I have tried to delete the files and reinstall and it won't work.