On Client Click is not working

Question

I have asp.net button--

<asp:Button ID="btnCommit" runat="server" Text='<%$ Resources:ZippSlipsResource, ViewForm_Commit %>'

                    CssClass="button green savensendbtn" OnClick="btnCommit_Click" OnClientClick="return ValidSave();"  />


My Java Script is-
-----------

  <script type="text/javascript">

        function ValidSave() {

            if (typeof (Page_ClientValidate) === "function")

                if (!Page_ClientValidate())

                    return false;

            if ($("span[id$='lblPayPalUserMissing']").attr("IsMissing") == "true" && $("input[id*='rblPaymentMode']:checked").val() == '<%= ZippSlips.Core.Model.Enums.PaymentMode.CreditCard %>') {

                $.blockUI({ message: $("div#MissingPaypalAccountError") });

                return false;

            }

            else if ($("#liMandatoryItemError").length > 0 && $(".paymentgrid").find("input[type='radio'],input[type='checkbox']").length > 0 &&

                        $(".paymentgrid").find("input[type='radio']:checked,input[type='checkbox']:checked").length == 0) {

                $("#liMandatoryItemError").removeClass("hide");

                return false;

            }

            else {

                return true;

            }

        }

    </script>

Problem is my Java Script code is not firing on Button click.
is any one have adea about this?