Smart App Control used to default to being off in new Windows installs, but is now being enabled by default, so this is becoming a more widespread problem. We are trying to resolve this problem by getting all our executable code signed by a trusted certificate (what is required by SAC). However, getting verified by Microsoft is going slowly.
Also note that before the latest Windows update, Smart App Control used to require a complete reinstall of Windows to re-enable. Make sure you are up-to-date on updates before trying that.