UI Dialog Problem

UI Dialog Problem


Hi together,
I want to use the Dialog Plugin. I use the examples from the
documentation (http://docs.jquery.com/UI/Dialog).
The only thing I do is to add some buttons like:
$('#foo').dialog({ width: 650, height: 300, buttons: { 'Ok':
function() { $(this).dialogClose(); }, 'Cancel': function() { $
(this).dialogClose(); } } });
When I click on a button the following error appears:
$.data(el, "ui-dialog") has no properties
http://localhost/Auswahl/jQuery/jquery.ui-1.0/ui.dialog.js
Line 130
Where is the problem?
Thanks
Kersten