>>Can you connect locally by using TCP/IP(i.e.: using localhost or the server's own IP)?

Just my 2c. We have also experienced this on a few PC's.

A connection string of:

localhost:c:\MyFolder\MyData.fdb

gives the connection rejected error.

Changing to:

c:\MyFolder\MyData.fdb

resolves the problem.

We haven't managed to get to the bottom of it yet, we usually just end up using the local connection string, but it would be nice to finally know what's causing it instead of using the workaround. Unfortunately, once the workaround is in effect, we then don't end up with much time to scrutinise the person's PC to find out what the problem was.