"this.placeholder is undefined" Error in jQuery UI 1.7.2

"this.placeholder is undefined" Error in jQuery UI 1.7.2

I know this error was supposed to be fixed in 1.6 RC5, but I'm still
having it. Here's the code if it will help:
$('#lnkCancelActivityAttributeSortOrder').click(function() {
        $('#ulActivityAttributes').sortable('cancel');
        $('.liAttributeItem').removeClass('sortableAttributeItem');
        $('#lnkSortActivityAttributes').show();
        $('#lnkSaveActivityAttributeSortOrder').hide();
        $('#lnkCancelActivityAttributeSortOrder').hide();
    });
I have re-downloaded 1.7.2 and overwritten all the files, to no avail.
Thanks
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