including jquery.ui 1.6 directly from theme.info
The correct way to include jQuery UI, from README.txt:

In your module, call the following function:

jquery_ui_add($files);


For example:

jquery_ui_add(array('ui.draggable', 'ui.droppable', 'ui.sortable'));
jquery_ui_add('ui.sortable');  // For a single file