color drop to 8 bit after Viruscanonline loads

[Claude S. Poliakoff]

Color display starts normally during boot up. After
picking myself for preference loading, McAfee viruscan
online loads. As soon as its little window completes,
screen blacks out momentarily, then comes back with
obvious degraded display (not safe mode). Manually
changing display prop color quality easily accomplished,
but not retained if re-boot needed for any reason.
Slightly annoying, & I'm sure fixable, but how?