fail to start

The game was working fine up until about yesterday dinner time. all of a sudden the exe. file was detected by anti virus and blocked. The game failed to launch after that. I allowed the app through the firewall but to no avail. I can verify the files on steam no problem but it still wont launch...

Gentlemen, help me, I sent bug reports, but so far it was dull, before installing patch 1.4.3 everything worked without problems, but after I installed the patch, the game began to fail to start with such an error, I never installed mods, cleaned the game cache, reinstalled, deleted all save...