Norton 360 turns off my computer before the scan is finished

When running a full system scan, at some point, Norton 360 turns off my
computer before the scan is finished.  This does not occur during a quick scan
and I do not have “Shut down computer” checked.  I ran Norton Power Eraser, and
when it found nothing, I rebooted in safe mode and ran the full system scan
without difficulty, and found no problems.  However, when I run it in the normal
mode Norton 360 still turns off my computer before the scan is finished.  What’s
left, reinstall?