Looks like the <a> tags are not very tall on the navigation menu. There is a 400ms delay that will keep the menu showing, but if you don't move fast enough the menu will go away.

gistfile1.txt

    jQuery('ul.sf-menu').superfish({
			delay:400, //looks like this is what is controlling the delay, maybe make it a little longer
//			pathClass:  'current-menu-item',
//			speed: 'fast',
	        autoArrows:  true,                           // disable generation of arrow mark-up 
            dropShadows: false  			
//			animation:   {opacity:'show'}			
			
		});