[jQuery] Accordion trouble

[jQuery] Accordion trouble

Hi all.
I've just found the Accordion plug-in and it seems pretty straight forward to implement but I get an "<span class="objectBox objectBox-errorMessage hasTwisty hasBreakSwitch opened">$(":first-child", this)[0] has no properties" in firebug when the page load and the navigation doesn't work. My code is really simple but maybe it could be thickbox or I'm just tired..
...
<script type="text/javascript" src="lib/jquery/jquery-compressed.js"></script>
<script type="text/javascript" src="lib/ThickBox/ThickBox.js"></script>
<script type="text/javascript" src="lib/Accordion/jquery.accordion.pack.js"></script>
<script type="text/javascript">
    $('#ulClubs').Accordion({
      header: 'a.club'
    });
...
                 <ul id="ulClubs">
                    <li>
                        <a class="club" href="#">Club majo</a>
                        <ul>
                            <li><a href="#">DJs</a></li>
                            <li><a href="#">Shows</a></li>
                        </ul>
                    </li>
                    <li>
                        <a class="club" href="#">En anden club</a>
                        <ul>
                            <li><a href="#">DJs</a></li>
                            <li><a href="#">Shows</a></li>
                        </ul>
                    </li>
                    <li>
                        <a class="club" href="#">En anden club</a>
                        <ul>
                            <li><a href="#">DJs</a></li>
                            <li><a href="#">Shows</a></li>
                        </ul>
                    </li>
                </ul>
Do any of your guys (and girls) see any problems in this (except from the fact that it doesn't work)?
Regards, Jon
</span>
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