There is nothing to walk through because we know squat about your system or any other technical details. Something has changed that's a given. Most likely another program has replaced a DLL. Could be a Windows Update, could be your virus scanner's daily updates or whatever. Either way, this is nothing that can be resolved by forum posts. Try to reinstall the software. Your serial number may be possible to find out by contacting support, since S&T registration is mandatory and they have your details.
Mylenium