A lot of programs in OS X only completely close if you select quit from one of the menus. I have a Canon scanner and the only way the scanning program will work is if i select quit; there isn't a keyboard shortcut. If that doesn't work chances are the icon to it is in the dock. You could control-click the icon and get a pop-up menu that has some commands on it. You can quit the program through that or if it's not responding it'll let you force-quit. Another way would be to hit command-option-escape which will bring up a task manager. And if it's like some programs I have encountered where you quit it and it stays in the dock, the only way you could really get rid of it would be to log out and log back in. Hope that helps you out a little.