After doing a very clean uninstalling of 8.1483 in safe mode and after two reboots, I installed 8.1489.
I rebooted and startup scan was running and during that, next thing I saw was a welcome screen from chrome and an enormous chrome updates ran.
OT: Even though I was doing Custom installation, how I missed the chrome checkmark, I don't know, I swear it wasn't there

I rebooted again and immediately went in to uninstall chrome.
I guess around that time Avast ran a definitions update, or another short scan, and a big red alert came on the screen about rootkits:
svc: gupdate > C:\Program
svc: gupdatem > C:\Program
See attached log and screenie - not sure if really rootkits or avast's internal error.
At some point, in my state of confusion by now, avast suggested boot scan, OK.
It went through all my partitions for hours. I don't think anything was found other that an item in a year-old copy of, all things, avast log I had in My Documents.
The aswAr.log upon next reboot looks clean.
I subsequently checked the web, and those two names, gupdate and gupdatem, seem to be related to that chrome varmin:
http://www.bleepingcomputer.com/startups/GoogleUpdate.exe-25791.htmlhttp://www.bleepingcomputer.com/startups/GoogleUpdate.exe-26582.htmlWhat do I do now? Do I really have a rootkit which bootscan didn't see? How to check? Is gmer still part of avast's scanner?