Cannot create iterator for this collection请问怎么解决？

页面上出现异常：Cannot create iterator for this collection请问怎么解决？
<%--用户管理   --%>  
<div   class= "menu_head "   id= "menu1 "   >
<a     class= "on "   id= "menu1_a "   tabindex= "1 "   onclick= "onoff(this);return   false "   onkeypress= "onoff(this) "> 用户管理 </a> </div>
<div   class= "menu_box "   id= "menu1_child ">
<table>
      <logic:present   name= "result ">
          <logic:iterate   id= "result "   name= "result ">
  <tr>
      <logic:equal   name= "result "   property= "pertain_to "   value= "a ">
  <td> <a   href= " <bean:write   name= "result "   property= "phref "   />   "> <bean:write   name= "result "   property= "pname "/> </td>
      </logic:equal>
      <logic:notEqual     name= "result "   property= "pertain_to "   value= "a ">
  <td> </td>
      </logic:notEqual>
  </tr>                  
          </logic:iterate>      
      </logic:present>
</table>
</div>    
<%--资料管理   --%>    
<div   class= "menu_head "   id= "menu2 "     >
<a       class= "on "   id= "menu2_a "   tabindex= "2 "   onclick= "onoff(this);return   false "   onkeypress= "onoff(this) "> 资料管理 </a> </div>
<div   class= "menu_box "   id= "menu2_child ">
    <table>
      <logic:present   name= "result ">
          <logic:iterate   id= "result "   name= "result ">
  <tr>
      <logic:equal   name= "result "   property= "pertain_to "   value= "b ">
  <td> <a   href= " <bean:write   name= "result "   property= "phref "   />   "> <bean:write   name= "result "   property= "pname "/> </a> </td>
      </logic:equal>
      <logic:notEqual     name= "result "   property= "pertain_to "   value= "b ">
  <td> </td>
      </logic:notEqual>
  </tr>                  
          </logic:iterate>      
      </logic:present>
      </table>
</div>

result有以下数据
phref                                               pname                       pertain_to