I've installed the game from the GOG downloader files. When i start the game, everything works fine, until few seconds from the apperance of the main menu.
Suddendly, a "downloadable content the bozak horde" message appears, and the game freezes.
Anyone has experienced this issue before?
I've already tried to verify game files, and uninstall/reinstall Diyng Light

This is the first thing that comes to my mind, so take it with a grain of salt.

The game tries to connect to the servers every time you launch it, even though it starts normally if you're offline and it's unable to reach them (it does so to check if there's any particular event going on or new content available). If your PC is online, make sure that the game can actually use your internet connection (check any active firewalls and stuff like that).