jquery.selectbox-0.5_style_2.js and javascript function issue

jquery.selectbox-0.5_style_2.js and javascript function issue

I am using - jquery.selectbox-0.5_style_2.js, to style my combo boxes. when i load this like this

<script type="text/javascript">
$(document).ready(function() {
    $('.styledselect_form_1').selectbox({ inputClass: "styledselect_form_1" });
    $('.styledselect_form_2').selectbox({ inputClass: "styledselect_form_2" });
});
</script>

I am getting the style properly. There is no problem on that. But javascript functions are not working on those comboxes. Example

<script type="text/javascript">
        $(document).ready(function(){
            // $("#txtDetailDescription").htmlarea();
            $("#cmbCategory").change(function() {
               
                var categoryId = $("#cmbCategory").val();
                $("#cmbSubCategory").load("<?php print($this->baseUrl());?>/ajex/sub-category/?catId="+categoryId);
                });
           
            $("#txtTelephone").mask("9999-99-9999999");
                        $("#txtMobile").mask("9999-99-9999999");


          

                    $("#txtAddTitle").keyup(function(event) {
                            title = $("#txtAddTitle").val();
                            title = title.toLowerCase();
                            title =  title.replace(" ","-");
                            $("#txtAddUrl").val(title);
                        });
                    });



        </script>

This is not working.  But when i remove these two lines -

   $('.styledselect_form_1').selectbox({ inputClass: "styledselect_form_1" });
    $('.styledselect_form_2').selectbox({ inputClass: "styledselect_form_2" });

Thats working. Can you pleas help to short it ?

Thanks
I.Iyngaran