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

[fambi]

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