If I try to open the file directly down the network...
Be careful, that can damage your file.
If you can see the server when you select Open Remote, but can't see the hosted file, see if this is the issue:
This is one of many acknowledged bugs that can be found in the Known Bug List here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: http://www.4shared.com/file/8orL8apk/FMP_Bugs.html
Thanks Phil. We will take a look at that and see if we can shed any light on it.