We saw this behavior a few times (4-5). Very frustrating to see your app working much faster when the database located on the secretary notebook rather than on the brand new server. Some of the reasons that come to mind were:

- antivirus (on the server and on the clients)
- backup systems trying to backup every time a file changes (web or local systems)
- network hardware problems (bad cables, switches, connectors)
- bad memory (bad DIMMs). Took months to find.