Serviio

Very recent upgrade to Serviio v1.8 freezes all the time when "saving the library".
When adding another shared folder to the library list, even nearly empty folders (tried several), the red save button becomes available but when saving it doe not finish its job.
I stopped the serviio service, restarted; no luck.
A reboot of pc does not work as well.
Switching off Metadata retreival does not help.

Everything worked well on previous pro version (1.6.x I believe). Please help!

I've had no such issue. I just had to rebuild my test server, so I did a fresh install of 1.8 and the library was populated within a matter of minutes. Of course, I only have about 300 files on that server, but didn't encounter any problems. I believe there were some internal changes to the database with 1.8, so upgrade installations might take some time after install to fully update the library.

It's possible that something corrupted your database during install. If you have the time, I suggest completely removing Serviio and trying a clean install.