jQuery("#startDate").datepicker is not a function

在主页上不好使，报错。导致以下的javascript,不运行。在测试界面就好使，我想知道什么原因。
我导入的顺序是
<script type="text/javascript" src="$base/js/jquery.js"></script>
<script type="text/javascript" src="$base/js/ui/js/jquery-ui-1.8.14.custom.min.js"></script>
<script type="text/javascript" src="$base/js/ui/ui/jquery.ui.datepicker.js"></script>
<script type="text/javascript" src="$base/js/ui/ui/jquery.ui.tabs.js"></script>
<script type="text/javascript" src="$base/js/ui/ui/jquery.ui.widget.js"></script>
<script type="text/javascript" src="$base/js/ui/ui/jquery.ui.core.js"></script>
<script type="text/javascript" src="$base/js/index/left.js"></script>
<script type="text/javascript" src="$base/js/index/middle.js"></script>
<script type="text/javascript" src="$base/js/index/right.js"></script>
<script src="$base/js/yzsl/frontPoint/oneVersionIndex1.js" type="text/javascript"></script>
<script type="text/javascript" src="http://www.variflight.com/embed/js/feeyoipto2.js" charset="gb2312"></script>
<script type="text/javascript" charset="gb2312">
_UID_ = "ZH86JMIdpv";
WebService.Flights.print("vflight");
</script>

是哪的错误呢？