Open up Paintbrush, in the dialog showing up right after launch enter an image size of 512x128, press Enter, hit Cmd+A (to select the entire canvas area), press Cmd+C to copy it to the clipboard, press Cmd+Alt+C to change the canvas size, enter 100x200 percent, press Enter. Paintbrush should crash at this point.
Snow Leopard, Paintbrush 2.1.1