How do I disable or enable 2nd dropdownlist in aspx based on selected choice of the 1st dropdownlist box

I am having a problem with disabling DropDownList based on the chice of 1st DropDownList, there is no post back occuring, and it is a template based web app here is the current code:

<script type="text/javascript">
   $(function() {  var dropDownList1 = $('#<%= ddlUserType.ClientID %>');
var dropDownList2 = $('#<%= ddlMember.ClientID %>');            dropDownList1.change(function(e)  {
if ( jQuery("#ddlUserType").val() != "ETOC")                           dropDownList2.removeAttr('disabled');                                     e.preventDefault();
      else 
      dropDownList2.removeAttr('enabled');                                    e.preventDefault(); }
     } );
      </script>

what is happening now is page is blank and if I remove the above code everything shows, where I am going wrong.

here is the plain and final javascript code which worked:

<script language="javascript">  
function CheckDropDownState(lstbox)
 { 
if (lstbox.selectedIndex == 3) {  document.forms[0].ddlMember.disabled = 1; }
else { document.forms[0].ddlMember.disabled = 0; } 
} 
</script>

and thew .aspx code:

<asp:dropdownlist id="ddlUserType" runat="server" onclick="CheckDropDownState(this);"></asp:dropdownlist>

Once again appreciate the help guys.

I've tried cleaning your code a little bit:

$(function() {  
    var dropDownList1 = $('#<%= ddlUserType.ClientID %>');
    var dropDownList2 = $('#<%= ddlMember.ClientID %>');            
    dropDownList1.change(function(e) {
        var selectedValue = $(this).val();
        if (selectedValue != 'ETOC') {
            // enable the second combo if the value selected in the first combo 
            // is not ETOC
            dropDownList2.removeAttr('disabled');
        } else {
            dropDownList2.attr('disabled', 'disabled');                                    
        }
        e.preventDefault(); 
    }
});