uncaught exception error "Illegal operation on WrappedNative prototype object"
<p>Any idea why the following javascript/jquery code might produce the error message:
uncaught exception: [Exception... "Illegal operation on WrappedNative prototype object" ?</p>

<p>Code:</p>

<pre><code>function deletereceipt(id){
 var $delconfdialog = $('&lt;div id="dialog-confirm"&gt;&lt;/div')
                       .html('Are you sure you want to delete this receipt?')
                       .dialog({
                          autoOpen: true,
                          title: 'Delete Confirmation',
                          buttons: {
                             "Delete": function(){
                                $.post('Receipt.py',{'cm':'Delete','receiptid': obj},function(){
                                   $('#receiptrow'+id).remove();
                                });
                                $(this).dialog('close');
                             },
                             "Cancel" :function(){
                                $(this).dialog('close');   
                             }
                          }
                       });
    }
</code></pre>
