Hy, just registered, I'm a total newby on j.s. having some problem with the plugin as well, you can see code and problem at this page (work in progress),
www.silentbreeze-yurt.com , what happens in firefox and some other browsers as well is that when the button up is pressed for a moment it blinks the header of page and then back to the movement ftom bottom up to top page, it's as if the link is followed first and then the plug in enters and perform the task afterwords,
Code:
<script>jQuery(function( $ ){
//borrowed from jQuery easing plugin
//http://gsgd.co.uk/sandbox/jquery.easing.php
$.scrollTo.defaults.axis = 'xy'; return false;
});</script>
and here is the html:
<div id="bottom">
<div id="up" >
<a href="#" onclick="$.scrollTo( '#header', 900 );">up</a>
</div>
</div> <!-- bottom -->