McAfee ruled out their software. I got to a second person at iLok who was just as mystified.
Finally, I went to my sync log in iLok, found the last date I synchronized, and restored my
system HDD to that date. Problem solved. I'm now working forward though system changes
to determine where the corruption occurs. If I find it I'll post again.
If you don't have a backup copy to restore, you might try upgrading/reinstalling your copy
of Windows.