Yes. The file should be opened on your Admin's PC with FileMaker Pro before you try to access the file with either another PC or from your iPhone. It may even be better in the long run to put this file on a third machine, opened with Filemaker so that these issues do not inconvenience your Administrator.
Thanks for the response. Thats what I was afraid of. As my Admin is part time it is impractical (and wasteful) to have the PC left running all the time.
Can I put my copy on our server, which is on all the time, allowing her to access/update data when required, and access it from my ipad using the Go app? For our extremely basic requirements I cant believe that we need to get Filemaker server?
It's unsafe to put the file on the server unless you also install Filemaker on the server and then open the file with FileMaker on that machine. Putting the file in a shared directory and then accessing it directly would appear to work, but it risks corrupting your database file.
See this KnowledgeBase article for more on the subject: http://help.filemaker.com/app/answers/detail/a_id/7616/kw/sharing