password will not work

[Dean]

we have a database that is used by many people it is
secured a when a user opens it a form/switchboard comes up
and they can do various things such as enter vaction. To
see all the tables queries reports etc we have use a
funtion button and a password. Out of the blue the the
function button opens password screen but will not let
you "in" password has not changed was working went back
in later and would not work.....help please!!!

Thanks
Dean