Redownloaded the game, verified game cache on steam and still have this problem, what is going on ?
After i updated it, this appeared.
If you download single player your problem will be fixed. However, they should fix it, as it wasn't and it shoudn't be necessary to have the singleplayer installed to play only multiplayer.
It doesn't work with the SP installed by me. It's the same error :/
There has been released a 5 GB update that fixes the problem. Now you can play multiplayer without having singleplayer installed.