I currently have a web site that is integrated with Active Directory using the MemberShip provider. Everything works fine and I can create/edit/ and change passwords for users. Occasionally a user gets hung and calling the ValidateUser method returns "The server is unwilling to process the request. (Exception from HRESULT: 0x80072035)" for a particular user. The only way around this is to delete and add the account again. Other users can continue to log in to the system.
Here is the method call : Membership.ValidateUser(uid, pwd);