Mac OS 10.8. I have the weirdest recurring problem. GIMP opens just fine, including any file, but I can't effect any change on the drawing itself. I can use the little % tab to zoom in, and the scroll bars to move around, but I cannot affect a single change within that window. Using filters does nothing, opening new files does nothing, closing and re-opening the program does nothing. Any ideas? Did I just press the "you're an idiot for touching this" button?