With the 1.7 release of dropdown menu widget, i changed the whole options page interface. Apparently i forgot to edit the template tag support for the new interface, that’s why sites using the template tag
<!--?php shailan_dropdown_menu(); ?--> were displaying vertical menus instead of horizontal. I fixed this issue with 1.7.1 version. Please update your plugin now to the latest version. Sorry for the inconvenience. Cheers..