Are you sharing this file? If so, have you provided a COPY of this file to each user and installed that file on their workstation? You should not share this file from a network resource (i.e. place it in a network folder and instruct users to run it from there). You should instead provide each user a copy of that file, and instruct them to run that local copy.
With the growing usage of Access 2007 and earlier versions in corporate envioronments, it's imperative that you properly handle this situation.