I think the behavior had stacked menuSlideUp and slideUp. I added a 'if' checking if the other function of sliding is not executed. http://jsfiddle.net/g7eYH/1/
correct code seems to be:
jQuery(document).ready(function(){
// Get window width + height
var windowWidth = $(window).width();
var windowHeight = $(window).height();
document.myslide=0;
$('#container1').css({
'width': windowWidth,
'height': windowHeight
});
// menu toggle
$('#menuBtnFake').hoverIntent({
over: menuSlideUp
});
$('#menu').mouseleave(function(){
if(document.myslide==0){
$(this).slideUp(500);
}else{
//double slide behavior occurs here
}
$('#contentFader').fadeIn(500);
});
$('#menuBtn').click(function(){
$('#menu').slideUp();
$('#contentFader').fadeIn(500);
});
});
function menuSlideUp(){
document.myslide=1;
$('#menu').slideToggle(500, function(){ document.myslide=0});
$('#contentFader').fadeOut(700);
}