I started a new world with around 2 hours of time on it and my screen suddenly froze, went blank for less than 20 frames (at most), and when the image came back some textures were both missing and miswrapped. I'm assuming that they are showing the default missing texture file. The tops and sides of cobblestone, grass, and dirt blocks have a rectangular mess of red, green, and blue boxes filling in where textures should be. Also my view is slightly below the normal block line now, so it looks as if I can see empty space between the top of a grass block and the dirt underneath.