Typing problem with jquery UI Autocomplete

I have problem with jquery ui Autocomplete... when i start typing words and while autocomplete is showing the results it just starts erasing letters before I even finish the word... anyone had this problem?

$(function() {
var rn = Math.floor(Math.random() * 11);
$("#query").autocomplete({开发者_开发百科
    source: "search.asp?rn=" + rn,
    minLength: 2,
    selectFirst: true,
    delay: 500,
    //autoFocus: true,
    select: function(event, ui) {
        var vp = ui.item.vp;
        var ran = Math.floor(Math.random() * 11);
        if (vp != "-1" && vp != "x") {
            location.href = "menu.asp?rn=" + ran + "&LOC=1&IDP=" + vp;
        }
        else if (vp == 'x') {
            location.href = "result.asp?rn=" + ran + "&term=" + ui.item.value;
        }
    }
});

$.ui.autocomplete.prototype._renderItem = function(ul, item) {
    var sterm = this.term.split(" ");
    $.each(sterm, function(index, value) {
        item.label = item.label.replace(new RegExp("(?![^&;]+;)(?!<[^<>]*)(" + $.ui.autocomplete.escapeRegex(value) + ")(?![^<>]*>)(?![^&;]+;)", "gi"), "<span style='color: #2779AA;'><strong>$1</strong></span>");
    });
    return $("<li></li>").data("item.autocomplete", item).append("<a>" + item.label + "</a>").appendTo(ul);
};

});

Are you using the autoFocus plugin? I had the same problem and fixed it with the solution described in:

https://github.com/scottgonzalez/jquery-ui-extensions/issues/1