// redefine Cycle's updateActivePagerLink function
$.fn.cycle.updateActivePagerLink = function(pager, currSlideIndex) {
    $(pager).find('li').removeClass('activeLI')
        .filter('li:eq('+currSlideIndex+')').addClass('activeLI');
};

$(function() {
    $('#slideshow').cycle({
        timeout: 3000,
        pager:  '#nav',
        pagerAnchorBuilder: function(idx, slide) {
            return '<li><a href="#"><img src="' + slide.src + '" width="40" height="53" /></a></li>';
        }
    });
});