I too have Bitdefender and whenever DCS World wants to update, it hangs, my computer is unusable (I can't launch anything else) and it stays that way until I do a reset.
Game mode doesn't solve the issue for me. In fact, I've had an issue with Bitdefender in the past with trying to install a game from Gamersgate. Even in game mode, Bitdefender would flag and quarantine the installer. Adding the installer to the exclusion list solved that particular issue.
I've added my Eagle Dynamics directory to the exclusion list. We'll see if that fixes it.
EDIT: That did indeed fix the issue for me.
