JQuery UI Autocomplete on IE6: open menu is rendered behind DropDownList control on page

JQuery UI Autocomplete on IE6: open menu is rendered behind DropDownList control on page

dear all,
i am using JQuery-UI Autocomplete on the page. beneath the autocomplete, there is a DropDownList.
 
when browsed on IE6 , and when i write inside the input field of the autocomplete, the suggestions menu opens successfully, but it gets rendered behind the DDL...
 
i added this style to the same page having the autocomplete and DDL, but with no success:
 
  1. .ui-autocomplete{position : relative; z-index: 100 !important;}
 
p.s. : it works fine on Chrome...
 
thanks