SharePoint 2010 CU August 13,2013
If you delete the sub site and still you are seeing the sub site's link in your root site collection,then its time for updating your SharePoint server with "August 13,2013 Cumulative update.
MS support site listing the another potential symptom of "Alert functionality in Claim based web application".
SharePoint 2010,August 13 CU,2013 - Download
MS support site listing the another potential symptom of "Alert functionality in Claim based web application".
SharePoint 2010,August 13 CU,2013 - Download