I've got five-year-old Apple iMac desktop computer, which is normally trouble-free. But yesterday I opened several pictures from a file on the desktop via the Preview app, and now they will not close. If you click on the button to close them, you just get an endless whirling little 'rainbow' circle. The only way to get rid of them is to do a force quit, because Preview is shown as not responding. When you open Preview again, these pictures immediately pop up again and cannot be removed, meaning you cannot access any other photos or even effectively use the computer. I've tried several restarts, but nothing works. Preview is obviously corrupted in some way. Has anyone got any suggestions for a quick solution?