Moving this discussion to the Photoshop General Discussion forum.
Could be a corrupt file, bad RAM, or a problem with your video card.
There is a way to see if this isn't a corrupt file, get another image editing software like paintdotnet, or just use one that comes with your mac. Open the file in the other editing software, and if it doesn't come up with the patterns then it's not corrupt. If it does, there is a problem with your video card and you might need to get it fixed.