Javascript表单提交:对象不支持此属性或方法(IE7)

我正在尝试使用javascript提交表单.Firefox工作正常,但IE在这个函数的提交行上抱怨"Object不支持这个属性或方法":

function submitPGV(formName, action)
{
    var gvString = "";

    pgVisibilities.each(function(pair) {
        gvString += pair.key + ":" + pair.value + ",";
    });

    $('pgv_input').value = gvString;

    var form = $(formName);
    form.action = action;
    form.submit();
}

叫这里:

// For getting element with id you must use # 
alert( typeof( $( '#ProductGroupVisibility' )));