the problem is that when i pass over a thumb too fast, the effect keeps blinking for a while...

Question

    ('.menu-nav li').hover(
       function() {
        $j(this).addClass("active");
        $j(this).find('.ulwrapper').stop(false, true).slideDown();
        $j(this).find('.ulwrapper .ulwrapper').stop(false, true).slideUp();
       },
       function() {
        $j(this).removeClass("active");        
        $j(this).find('div').stop(false, true).slideUp('fast');
       }
      );
      $j('.ulwrapper').hover(
       function() {
        $j('.parent').addClass("active_tab");
       },
       function() {


 $j('.parent').removeClass("active_tab");        
   }

Answer 1

This may or may not solve your problem:

http://cherne.net/brian/resources/jquery.hoverIntent.html