Same problem for me. With Nod32 V7, on Windows 8.1 Metro Apps quit working. After uninstalling Nod32, Metro Apps work again. If I reinstall Nod32, Metro Apps quit working. I have installed and uninstalled Nod32 V7 many times with the same results every time. The only solution for me to have Metro Apps working with Nod32 is to disable HIPS.