Had one recently tell me that he had problems logging in. Asked him what the error was, it seemed to confuse him. The kind of blank look usually associated with there being no error box because its not even got a login box.
Had to go to his desk to find out what the problem was. He had been typing his username incorrectly. The same username he has been using for years.
I should take the Dogbert approach of giving people like him abuse so no one wants to come ask for help.