Just back from a month away, switched on Photoshop which started okay, but then won't let me upload an image. Instead I get the screen flashing black and white at me continuously. I have tried closing down and restarting my computer (Dell PC). That didn't work. I've uninstalled Photoshop and reinstalled it. Still same problem. Photoshop is working on my laptop however, so why not on the PC. Can anyone help?