I will be working on a file, and have several files open at the same time, when I drag a layer over from another file the entire file will go either all black or all white. When I click on the top of the file I can see that the layer is there but when I click in the middle of the file it is white or black. I have to close down all of Photoshop and redo and sometimes that doesn't even solve the problem. Very frustrating.