Today I have dedicated my time to first running the AVG in Safe Mode for the user Administrator, and tried the update with the browser, but it still wouldn't work. Secondly, I ran the AVG in Safe Mode for the my user, tried the update and it also still didn't work.
In Safe Mode, AVG runs in the command prompt mode. It mentions that parameters can be used. Watching as it scanned it appeared that the main culprit is tribalfunsion.com.
Anyway, I looked in the Help section of AVG, about parameters; those interesting me most were /scan, /clear, and /boot, which boot checks the boot sector, if I'm thinking clearly.
Was this the reference you alluded to earlier?
From Safe Mode, since the AVG program doesn't open, just the command line mode, I couldn't get to the Administrator's Windows AVG to empty a vault, etc. With my user Windows AVG, I was able to do that. This doesn't take care of Administrator's files.
If the /boot switch used is for checking the boot sector, then I will try it. Each scan takes almost 3 hours each.