[jQuery] jQuery BlockUI and ASP.NET

[ALBO]

Good day guys,
I'm tring to integrate jQuery blockUI plugin in my .net pages.
Basically I added this js code, first of all:

<script type="text/javascript">
    $().ajaxStop($.unblockUI);
    function test() {
                $(document).ready(function() {
                        $('#xxx').ajaxForm(function() {
                alert("Thank you for your comment!");
            });
                });
    }
    $(document).ready(function() {
        $('#btnSearch').click(function() {
            $.blockUI('<img src="gfx/ico-busy.gif" /> Searching,
please wait...');
            test();
        });
        var messageElement = $('#domMessage');
    });
</script>

My form looks like:

<form name="ctl01" runat="server" id="xxx">
...
<asp:ImageButton id="btnSearch" ImageUrl="gfx/btn_search.gif"
OnClick="clk_search" runat="server"/>
</form>

where "clk_search" is the method that submit the form.
With this code, my loading message box appears but no submit has made.
What's wrong?

thanks
alberto