Very strange indeed. When I try to start a mission, i get: "Download of Tutorial - Running Start r383 failed.". If I select a map and the game actually starts to load, it freezes at 10% loading weapons definitions (i think that is what it said). A few clues are
1. It started after I updated to the new lobby.
2. I just updated to windows 10.
3. Another open source game, Warzone 2100, is also broken.
4. All other games on my system work fine with steam.
Any help would be appreciated, thanks.