This is unlikely to be a Word or VBA issue, since it is working for your other users. Rather, it is more likely to be an issue with network permissions and/or what the ReportDir variable is being populated with.
PS: For cross-posting etiquette, please read:
http://www.excelguru.ca/content.php?184. You need to provide links between the two sites, so anyone looking at the issue on either can take into account what has been said on the other.