[jQuery] Difficult to describe issue relating to selects!!!

[jQuery] Difficult to describe issue relating to selects!!!


We nest our form inputs into unordered lists and use jquery to
highlight the parent list item of the active input:
$(function()
{
    $("ul.form").find("input,select,textarea,option,.file")
    .focus
    (
        function()
        {
            $(this).parents('li').addClass('ShowGuidelines');
        }
    )
    .blur
    (
        function()
        {
            $(this).parents('li').removeClass('ShowGuidelines');
        }
    );
});
One interesting problem which we're facing is that, when selecting a
select box, rather than bring down the list of options, it simply
focuses on the select box and we then need to click again to bring the
list down (i.e. 2 clicks needed instead of one!)
If the addClass is replace with css(etc.), it works fine.
Anyone have any idea what's going on???
Thanks