I had the exact same issue with my Flip13. Had it hooked up to the TV to watch a movie, so I wasn't even physically using it, then I closed it and placed it in my book bag. Pull it out the next day and open the screen to find a several cracks emanating from the side. This is a padded book bag for laptops...there was nothing in it to cause the crack. These screens are just so flimsy!
Very unhappy. Had to disable touch capabilities so I can use it.