javascript hide problem

[ragtek]

i've made an ajax profileditor

http://www.ragtek.org/tutorials/editor.htm
the fields are coded like this:

<div class="smallfont"><span id="usertitle">test</span></div>Einladungen: <span id="einladungen">200</span>

now when i want to edit the "Einladungen" field, its working fine
but for usertitle im getting this error:

usertitle.style has no properties
[Break on this error] usertitle.style.display = '';

the strange thing is:

usertitle.style.display = 'none'; is working,
usertitle.innerHTML = xml_sender.fetch_data(fetch_tags(xml_sender.handle r.responseXML, 'linkhtml')[0]); is also working,
but usertitle.style.display = ''; isn't working

the fields are updated, just the showpart isn't working :/