I just upgraded my Ubuntu version from 10.04 to 12.04. When I click a Launcher icon, such as Firefox (just an example), the application will not start. To start the application, I need to right click on the icon then click on the name of the application to get it started. The application always starts when I right click first then click on the name, but does not start when I simply click on the icon. Any help would be appreciated.