I just installed MC15 build 28, coming from build 20. I am now unable to connect to my Media Server, which is running build MC14 build 155. This arrangement worked fine when running MC15 build 20. Now when connecting, I immediately receive the classic:
"Media Center failed to load the library 'X' and will attempt to load the previously selected library."
The client behaved as if I wasn't authenticating correctly, so I removed authentication on the server and restarted to no effect. The server log wasn't even showing any connection attempts. I backed off to MC 15 build 20 on my client, and now I'm able to connect again.
FYI - The reason I'm running MC14 on the server side is that I connect from a number of clients (work/home/laptop), and I want the server to remain on a production build of MC.