We have had multiple instances of queries becoming corrupted. The suggested fix is to remove all users access to the query, then delete and recreate the query, then reassign access. The query cannot be deleted if it is assigned to a user. There is no way to search to see which users have access to a query and we have 234 users in our system, so I had to open each user that might have had access to the query and see if it was assigned, then after I found a user, try deleting it again. It's a tedious process that could be and should be automated by either listing who has access when trying to delete a query or perhaps even better from an auditing perspective, allow reporting based on who has access to a given query.