You are using a 'file server' - not FileMaker Server ?
If You copy one of the files (just for testing! Do not work with it!) to the local drive: Is it working?
If so: You might check the firewall
The File works if it is located on the system itself. Firewall is part of the F-Secure PSB Workstation Security. I think the problem lies in this. Thanks. Ill troubleshoot and let you know how it goes.