Rwcoll, as soon as a new version comes out, I always upgrade BOTH my client(s) and server. If there's quirks in the build that cause things to not work for me, I go back to the previous build and wait for the next...
I have not had any real dramas using Media Server for some time, although occassionally, a build will come out where things like the client not receiving album cover art or something weird happens.
As I tend to install new versions over the top of exisiting ones, in these sorts of cases I will bite the bullet, and do an uninstall first, then a fresh install, and completely rebuild my database. Sometimes this seems neccessary.
It seems a lot of people get upset when they are forced to do stuff like this, but reall, how much of a big deal is it? If all your tags are good, rebuilding the database is a minor hassle.
I did this the other night, and my library of 13000 songs was imported into the library in about 5 minutes. I think the newer versions have had some tweaking done, as this is the fastest importing I have seen yet of my collection. (I'm sure it helps, too, that all my MP3s are sitting on a 175Gb RAID-5 Array!!).
Rwcoll, You said "My library on the client was gone". The library never really exists on the client; each time you fire up the client, it finds the server and "downloads' the library before opening up.
I also use DHCP assigned addreses, using a Linux (IPCop) firewall on my network, and it makes no difference.
I think if you accept the JRiver feller's advice, and make sure both ends are running the same version, you might find things run much smoothier!!