bug with ui.resizable in FF

in firefox 2 and 3, if I do this

....

<script type="text/javascript" src="js/jquery.js"></script>

<script type="text/javascript" src="js/ui/ui.core.js"></script>

<script type="text/javascript" src="js/ui/ui.resizable.js"></script>

<script type="text/javascript">

$(document).ready(function(){

$("th").resizable();

});

</script>

...

...

<table>

<thead>

<tr>

<th>col 1</th> <th>col 2</th>

</tr>

</thead>

<tbody>

<tr>

<td>foo</td><td>bla bla</td>

</tr>

<tr>

<td>fooo</td><td>blabla bla</td>

</tr>

</tbody>

</table>

the box for resize go to the right and the bottom (default option)

I try changing the options, whitout own css sheet, but doesn't work

in IE7 work ok