-text_field_with_auto_complete- browser problems

Hello, i'm using the following code in my rails app. works like a charm on IE. but on FF no autocomplete popup is displayed. can somebody help?

rails code: <p>     <%= text_field_with_auto_complete :person, :nachname, {},     {      :select => 'name',      :after_update_element =>        "function(element,value) " +        "{ " +        remote_function(:update=>'Kundendaten',          :url=>{:action=>:update_kundendaten},          :with=>"'adr_id='+value.id") + ";" +        "}"     } %> </p>

html result: <p>    <style> div.auto_complete {              width: 350px;              background: #fff;            }       div.auto_complete ul {              border:1px solid #888;              margin:0;              padding:0;              width:100%;              list-style-type:none;            }      div.auto_complete ul li {              margin:0;              padding:3px;            }      div.auto_complete ul li.selected {              background-color: #ffb;            }      div.auto_complete ul strong.highlight {              color: #800;              margin:0;              padding:0;            } </style>

<input id="person_nachname" name="person[nachname]" size="30" type="text" /> <div class="auto_complete" id="person_nachname_auto_complete"></div>

<script type="text/javascript"> //<![CDATA[ var person_nachname_auto_completer = new Ajax.Autocompleter('person_nachname', 'person_nachname_auto_complete', '/vermietung/auto_complete_for_person_nachname', {afterUpdateElement:function(element,value) { new Ajax.Updater('Kundendaten', '/vermietung/update_kundendaten', {asynchronous:true, evalScripts:true, parameters:'adr_id='+value.id});}, select:'name'}) //]]> </script> </p>