Uncheck group checkbox if at least one in group is unchecked w/jQuery
var checkboxes = $("#myTable input[type=checkbox:enabled]:not(:first)").change(function() {
    var allIsChecked = checkboxes.length === checkboxes.filter(":checked").length;
    all[0].checked = allIsChecked;
});

var all = $("#checkAll").change(function() {
    checkboxes.attr("checked",this.checked);
});

var $checkboxes =
    $("#myTable input[type=checkbox]:not(:first)").
        not($("#myTable input[disabled=disabled]")).
        change(function() {
            var allIsChecked = $checkboxes.length === $checkboxes.filter(":checked").length;
            $all[0].checked = allIsChecked;
});

var $all = $("#checkAll").change(function() {
    $checkboxes.attr("checked", this.checked);
});

var checkboxes = $("#myTable input[type=checkbox]:not(:first)");
checkboxes.change(function() {
  var allIsChecked = checkboxes.filter(:enabled:not(:checked)).size() === 0;
  all[0].checked = allIsChecked;
});

 var all = $("#checkAll").change(function() {
  checkboxes.filter(":enabled").attr("checked",this.checked);
});