Please try to add this code to your page.
<script type="text/javascript">
(function($){
function inputEventHandler(e){
var target = e.data.target;
var t = $(target);
var state = t.data('combo');
var opts = t.combo('options');
if (opts.editable){
if (state.timer){
clearTimeout(state.timer);
}
state.timer = setTimeout(function(){
var q = t.combo('getText');
if (state.previousText != q){
state.previousText = q;
t.combo('showPanel');
opts.keyHandler.query.call(target, q, e);
t.combo('validate');
}
}, opts.delay);
}
}
$.extend($.fn.combo.defaults.inputEvents, {
input: inputEventHandler
});
})(jQuery);
</script>