If the programs worked yesterday, and you haven't update them, it's fairly obvious it can't depend from them, they surely don't self-modify and they don't self-update if you don't launch the updater, and we surely haven't changed neither the Addon Manager.dll nor the Couatl.exe file, so even if you did launch the Live Update, it would have downloaded exactly the same version which was online yesterday.
So no, what you are describing can't happen, must be something external, most likely the antivirus, it wouldn't be the first time we heard of antivirus products so bugged, they even block programs that you explicitly allowed, without giving any notice.
I can only suggest to switch to a more reliable antivirus, like the free MS Security Essentials, which doesn't mistakenly detect our software as a threat to begin with, without requiring any configuration.