Removing class

Removing class

Hi everyone...

Im learning jquery actually, so i guess im a dumbie 8) ... anyone can help me?

I have a little unordered menu (UL > LI > UL > LI) and in the first LI layer, all that elements have one class 'categoria'.

When my mouse over, i put a class on a child-element A (class 'ativo')... its all working! butttttt....

when i leave the menu, i wanna remove that class again... for back to normal...

its working:
$(document).ready(function() {
    $("#nav li.categoria").hover(function() {
        $(this).children("a").addClass("ativo");
    }, function() {
});


isnt working:
$("#nav li ul").mouseout(function() {
        $("#nav li").removeClass("ativo");
    });




ps: sorry for my english, im from Brazil, and i'm not very adapted to other languages