Trying to remember the details for what is a very old version of Filemaker....
5.5 supports multiple network protocols, not just TCP/IP as is the case with newer versions. If you dn't use TCP/IP as your network protocol, you may need to check and see what has been specified for networking protocols on your new server to make sure that they match to what your client machines are set up for.
No, I've always used IPX/SPX (FMServer 5.5 supports both IPX/SPX and TCP/IP).
I got it working: I had rebooted several times, with no change, but I finally shut the machine completely down, and left it off for a few minutes before starting it up again. Suddenly it works fine. Coincidence? Or is there something in FMServer (or Windows Networking) that doesn't completely reset unless you do a 'hard' restart?
You are running FMS on a machine that is also now being used as a fileserver? As I understand it, that is bad policy. One thing you might check for is port conflicts.
Bad policy? I'd always read that you're supposed to run FMS on a computer dedicated to that purpose (am I mis-using the term "file server"? Ours runs Windows XP as a peer in our LAN, not a "server/client" OS setup)
However, our server machine also hosts a windows "shared" folder (for simple file-sharing across the LAN) and some IMAP mail folders (using Mercury Mail). These might slow it down a little, but otherwise shouldn't cause any real trouble, right?
I've seen some discussion of "port conflicts" online, but I'm not really sure what they are or how to check for them - but I got the impression they were only applicable to accessing FM files over the internet. Ours are only used on our in-house Ethernet LAN.
Forgive my ignorance - we are a small company with no IT staff. I do it all, but I'm a bookkeeper who had a little technical education in the 80s