Overdues: "I never checked it out"

[Thomas Neil Tomporowski <ttomporo@PERHAM.CFA.ORG>]

lm_net people

An ethics question of sorts:

If your computer shows a student having a book checked out and the student claim
 s she/he never checked out the book, what do you do?  No staff is infallible an
 d so the error could be on our end when checking out the book; however, in most
  cases I suspect the students may have simply forgotten they checked out the bo
 ok or are prevaricating.  While I am loath to make judgements about any student
 's honesty, I do have a system whereby I give them the benefit of the doubt the
  first time an incident happens and if the same thing happens again with the sa
 me student, I require them to pay for the book before any more books can be che
 cked out.  This whole issue is important to me (and, I suspect, to many other l
 ibray media professionals) as it involves ethics in our dealings with our clien
 ts.  Any experiences from your arena would be welcome.  I'll post a <hit> if en
 ough people show an interest in this issue.