一个JS选择地市的问题！请高手解决？
大侠们：
  我做了一个选择地市的功能！可是每次我将鼠标移动到地市的时候，就自动隐藏了地市选择的DIV，我搞不明白什么回事，大家看看我的代码哪里有问题。

------------------------------以下是HTML代码-----------------------------------------------
<div class="changeCity" id="changeCity" onmouseout="hideChooseCity(this)"><!-- class="micon" 去掉样式 -->
  <!-- [--><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="" style="background-position: -254px -131px;"></span></span><!-- ] --><br>
  <!-- [--><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="" style="background-position: -254px -131px;"></span></span><!-- ] -->
  <div class="city_change_jt" id="city_change_jt" style="position:relative;" onmouseover="showChooseCity();">
  <input type="hidden" name="cityCode" id="cityCode" value="${cityCode}">
  <a class="area-side" href="#" style="cursor:pointer;color:#ff6600" id="cityShow" onclick="aa('div_area',0)">
  <c:choose> 
  <c:when test="${'0792' == cityCode}">九江</c:when>
  <c:when test="${'0793' == cityCode}">上饶</c:when>
  <c:when test="${'0794' == cityCode}">抚州</c:when>
  <c:when test="${'0795' == cityCode}">宜春</c:when>
  <c:when test="${'0796' == cityCode}">吉安</c:when>
  <c:when test="${'0797' == cityCode}">赣州</c:when>
  <c:when test="${'0798' == cityCode}">景德镇</c:when>
  <c:when test="${'0799' == cityCode}">萍乡</c:when>
  <c:when test="${'0790' == cityCode}">新余</c:when>
  <c:when test="${'0701' == cityCode}">鹰潭</c:when>
  <c:when test="${'0791' == cityCode}">南昌</c:when>
  <c:otherwise>切换地区</c:otherwise>
  </c:choose>
  <img id="a_area" name="a_area" onclick="" src="${contextPath }/images/city_down.jpg" />]</a>
  </div>
   
  <!--隐藏层，地市列表 begin -->
  <div style="DISPLAY: none;position: absolute; z-index: 3;width: 220px" onmouseenter="showChooseCity();" id="div_area" name="div_area" class="city-show">
 
<H3>请选择地区</H3>
<li class="style2">
<a href="#" onclick="fuc_setcity_v3logo('南昌','0791');" style="cursor:hand;">南昌</a>
<a href="#" onclick="fuc_setcity_v3logo('九江','0792');" style="cursor:hand;">九江</a>
<a href="#" onclick="fuc_setcity_v3logo('上饶','0793');" style="cursor:hand;">上饶</a>
<a href="#" onclick="fuc_setcity_v3logo('抚州','0794');" style="cursor:hand;">抚州</a>
<a href="#" onclick="fuc_setcity_v3logo('宜春','0795');" style="cursor:hand;">宜春</a>
<a href="#" onclick="fuc_setcity_v3logo('吉安','0796');" style="cursor:hand;">吉安</a>