Thanks again -- it's not a hidden folder/files issue; the way the software organizes itself has changed. I've actually got a parallel thread with up-to-date info on what needs to be deleted/recreated over here
But I'm starting with the reinstall. Failing that, I'll try this updated information: move EppOobe.etl in C:\ProgramData\Microsoft\Microsoft Security Client\Support\ to a backup folder and let it repropagate.
Thanks for the quick reply!