[jQuery] sliding menu - sliding problem

i am having trouble making my menu transition smoothly between
sections as i click.
i added the last line of code to this JS in order to automatically
close sections as i click on a new section (the original code did not
have it on the first and last lines); if i have "A" open and click on
"B", "A" jerks closed instead of smoothly closing as "B" opens. i am
100% n00b on this stuff so any assistance would be greatly
appreciated.
thanks in advance!!
$(document).ready(function()
{
    // First we hide all exhibitis
    $("#menu ul li.section-title").nextAll().hide();
    // then the active exhibit is showed
    $("#menu ul").each(function(){
    $(this).find("li.active").prevAll().nextAll().show();
    });
    //This is the toggle function
    $("#menu ul li.section-title").click(function(){
    $(this).nextAll().slideToggle("fast");
    $("#menu ul li.section-title").nextAll().hide();
    });
});