Decided to use NRT, rebooted, installed NIS 20.2.1, ran liveupdate (must have had to reboot at least 3 times) but eventually everything was up to date. Within half an hour, Autofix ran on its own accord and reported 3048,3. There was no indication of the cause. I have added no new hardware, there are no yellow exclamation marks. Machine is Dell running XP SP3.