Oh, If I install the 1,7 prelease on my dedicated server, would I then have to install 1,7 prerelease on all of my clients (never had to do this on previous releases)?You need to run the same Version on Client and Server.
Short answer is it should actually be fine with the 1.6.0 server, although it will log the fact that there is a different version.
Since you have not provided logs, we can't possibly work out why it isn't working for you.
Need a bug report in the proper section of the forum.
https://forum.team-mediaportal.com/forums/1-7-0-pre-release.673/
Thanks!